cvs: phpweb / zend-engine-2.php
| From: | Gabor Hojtsy | Date: | Sat, 02 Aug 2003 14:25:00 +0000 |
| Subject: | cvs: phpweb / zend-engine-2.php | ||
| Groups: | php.mirrors | ||
| Request: | Send a blank email to php-mirrors+get-19745@lists.php.net to get a copy of this message | ||
goba Sat Aug 2 10:25:00 2003 EDT
Modified files:
/phpweb zend-engine-2.php
Log:
Whitespace fixes and adding <code> where it was missing
Index: phpweb/zend-engine-2.php diff -u phpweb/zend-engine-2.php:1.11 phpweb/zend-engine-2.php:1.12 --- phpweb/zend-engine-2.php:1.11 Mon Jul 28 04:31:37 2003 +++ phpweb/zend-engine-2.php Sat Aug 2 10:25:00 2003 @@ -1,5 +1,5 @@ <?php -// $Id: zend-engine-2.php,v 1.11 2003/07/28 08:31:37 goba Exp $ +// $Id: zend-engine-2.php,v 1.12 2003/08/02 14:25:00 goba Exp $ $_SERVER['BASE_PAGE'] = 'zend-engine-2.php'; include_once $_SERVER['DOCUMENT_ROOT'] . '/include/prepend.inc'; commonHeader("Changes in PHP 5/Zend Engine 2.0"); @@ -7,33 +7,38 @@ <h1>Changes in PHP 5/Zend Engine 2.0</h1> -<p>[ <a href="http://www.nexen.net/interview/index.php?id=32" target="_blank">Disponible en français</a> ]</p> +<p> + [ <a href="http://www.nexen.net/interview/index.php?id=32" target="_blank">Disponible + en français</a> ] +</p> <h2>New Object Model.</h2> <p> -PHP's handling of objects has been completely rewritten, allowing for better performance and more -features. In previous versions of PHP, objects were handled like primitive types (for -instance integers and strings). The drawback of this method was that semantically the whole object -was copied when a variable was assigned, or pass as a parameter to a method. In the new approach, -objects are referenced by handle, and not by value (one can think of a handle as an object's -identifier). + PHP's handling of objects has been completely rewritten, allowing for better + performance and more features. In previous versions of PHP, objects were + handled like primitive types (for instance integers and strings). The drawback + of this method was that semantically the whole object was copied when a + variable was assigned, or pass as a parameter to a method. In the new approach, + objects are referenced by handle, and not by value (one can think of a handle + as an object's identifier). </p> <p> -Many PHP programmers aren't even aware of the copying quirks of the old object model and, therefore, -the majority of PHP applications will work out of the box, or with very few modifications. + Many PHP programmers aren't even aware of the copying quirks of the old object + model and, therefore, the majority of PHP applications will work out of the box, + or with very few modifications. </p> <h2>Private and Protected Members</h2> <p> -PHP 5 introduces private and protected member variables, they allow you to define the visibility of class -properties. + PHP 5 introduces private and protected member variables, they allow you to + define the visibility of class properties. </p> <h3>Example</h3> <p> -Protected member variables can be accessed in classes extending the class -they are declared in, whereas private member variables can only be accessed -by the class they belong to. + Protected member variables can be accessed in classes extending the class + they are declared in, whereas private member variables can only be accessed + by the class they belong to. </p> <p> <?php highlight_string('<?php @@ -76,7 +81,7 @@ <h2>Private and protected methods</h2> <p> -With PHP 5 (Zend Engine 2), private and protected methods are also introduced. + With PHP 5 (Zend Engine 2), private and protected methods are also introduced. </p> <h3>Example</h3> @@ -106,15 +111,15 @@ </p> <p> -Old code that has no user-defined classes or functions named "public," "protected" -or "private" should run without modifications. + Old code that has no user-defined classes or functions named "public", + "protected" or "private" should run without modifications. </p> <h2>Abstract Classes and Methods</h2> <p> -PHP 5 also introduces abstract classes and methods. An abstract method only declares the -method's signature and does not provide an implementation. A class that contains abstract -methods needs to be declared abstract. + PHP 5 also introduces abstract classes and methods. An abstract method + only declares the method's signature and does not provide an implementation. + A class that contains abstract methods needs to be declared abstract. </p> <h3>Example</h3> <p> @@ -135,15 +140,15 @@ </p> <p> -Abstract classes cannot be instantiated. Old code that has no user-defined classes or -functions named 'abstract' should run without modifications. + Abstract classes cannot be instantiated. Old code that has no user-defined + classes or functions named 'abstract' should run without modifications. </p> <h2>Interfaces</h2> <p> -The Zend Engine 2.0 introduces interfaces. A class may implement an arbitrary list -of interfaces. + The Zend Engine 2.0 introduces interfaces. A class may implement an arbitrary + list of interfaces. </p> <h3>Example</h3> @@ -161,14 +166,15 @@ </p> <p> -Old code that has no user-defined classes or functions named 'interface' or -'implements' should run without modifications. + Old code that has no user-defined classes or functions named 'interface' or + 'implements' should run without modifications. </p> <h2>Class Type Hints</h2> <p> -While remaining loosely typed PHP 5 introduces the ability to use class type hints to declare -the expected class of objects that are passed as parameters to a method. + While remaining loosely typed PHP 5 introduces the ability to use class type + hints to declare the expected class of objects that are passed as parameters + to a method. </p> <h3>Example</h3> <p> @@ -199,8 +205,8 @@ ?>'); ?> </p> <p> -These class type hints are not checked upon compilation, as would be the case -in a typed language, but during runtime. This means that: + These class type hints are not checked upon compilation, as would be the case + in a typed language, but during runtime. This means that: </p> <p> <?php @@ -212,7 +218,7 @@ ?> </p> <p> -is equivalent to: + is equivalent to: </p> <p> <?php @@ -225,13 +231,13 @@ ?>'); ?> </p> <p> -This syntax only applies to objects/classes, not built-in types. + This syntax only applies to objects/classes, not built-in types. </p> <h2>final</h2> <p> -PHP 5 introduces the "final" keyword to declare final members and methods. Methods and -members declared final cannot be overridden by sub-classes. + PHP 5 introduces the "final" keyword to declare final members and methods. + Methods and members declared final cannot be overridden by sub-classes. </p> <h3>Example</h3> <p> @@ -244,27 +250,28 @@ ?>'); ?> </p> <p> -Old code that has no user-defined classes or functions named 'final' should run -without modifications. + Old code that has no user-defined classes or functions named 'final' should + run without modifications. </p> <h2>Object Cloning</h2> <p> -PHP 4 (Zend Engine 1.0) offered no way a user could decide what copy constructor to run -when an object is duplicated. During duplication, PHP 4 did a bit for bit copy making an -identical replica of all the object's properties. -</p> -<p> -Creating a copy of an object with fully replicated properties is not always the wanted -behavior. A good example of the need for copy constructors, is if you have an object which -represents a GTK window and the object holds the resource of this GTK window, when you -create a duplicate you might want to create a new window with the same properties and have -the new object hold the resource of the new window. Another example is if your object holds -a reference to another object which it uses and when you replicate the parent object you want -to create a new instance of this other object so that the replica has its own separate copy. + PHP 4 (Zend Engine 1.0) offered no way a user could decide what copy constructor + to run when an object is duplicated. During duplication, PHP 4 did a bit for bit + copy making an identical replica of all the object's properties. +</p> +<p> + Creating a copy of an object with fully replicated properties is not always the + wanted behavior. A good example of the need for copy constructors, is if you have + an object which represents a GTK window and the object holds the resource of this + GTK window, when you create a duplicate you might want to create a new window with + the same properties and have the new object hold the resource of the new window. + Another example is if your object holds a reference to another object which it + uses and when you replicate the parent object you want to create a new instance + of this other object so that the replica has its own separate copy. </p> <p> -An object copy is created by calling the object's <code>__clone()</code> method: + An object copy is created by calling the object's <code>__clone()</code> method: </p> <p> <?php highlight_string('<?php @@ -272,13 +279,14 @@ ?>'); ?> </p> <p> -When the developer asks to create a new copy of an object, the Zend Engine will check if a -<code>__clone()</code> method has been defined or not. If not, it will call a default <code>__clone()</code> -which will copy all of the object's properties. If a <code>__clone()</code> method is defined, -then it will be responsible to set the necessary properties in the created object. For convenience, -the engine will supply a function that imports all of the properties from the source object, so -that they can start with a by-value replica of the source object, and only override properties that -need to be changed. + When the developer asks to create a new copy of an object, the Zend Engine will + check if a <code>__clone()</code> method has been defined or not. If not, it + will call a default <code>__clone()</code> which will copy all of the object's + properties. If a <code>__clone()</code> method is defined, then it will be + responsible to set the necessary properties in the created object. For + convenience, the engine will supply a function that imports all of the properties + from the source object, so that they can start with a by-value replica of the + source object, and only override properties that need to be changed. </p> <h3>Example</h3> <p> @@ -315,19 +323,22 @@ <h2>Unified Constructors</h2> <p> -The Zend Engine allows developers to declare constructor methods for classes. Classes -which have a constructor method call this method on each newly-created object, so it is -suitable for any initialization that the object may need before it is used. -</p> -<p> -With PHP 4, constructor methods were class methods that had the same name as the class itself. Since -it is very common to call parent constructors from derived classes, the way PHP 4 worked made it a bit -cumbersome to move classes around in a large class hierarchy. If a class is moved to reside under a -different parent, the constructor name of that parent changes as well, and the code in the derived class -that calls the parent constructor has to be modified. + The Zend Engine allows developers to declare constructor methods for classes. + Classes which have a constructor method call this method on each newly-created + object, so it is suitable for any initialization that the object may need + before it is used. +</p> +<p> + With PHP 4, constructor methods were class methods that had the same name as + the class itself. Since it is very common to call parent constructors from derived + classes, the way PHP 4 worked made it a bit cumbersome to move classes around + in a large class hierarchy. If a class is moved to reside under a different + parent, the constructor name of that parent changes as well, and the code in + the derived class that calls the parent constructor has to be modified. </p> <p> -PHP 5 introduces a standard way of declaring constructor methods by calling them by the name <code>__construct()</code>. + PHP 5 introduces a standard way of declaring constructor methods by calling + them by the name <code>__construct()</code>. </p> <h3>Example</h3> <p> @@ -350,23 +361,26 @@ ?>'); ?> </p> <p> -For backwards compatibility, if PHP 5 cannot find a <code>__construct()</code> function -for a given class, it will search for the old-style constructor function, by the name of the -class. Effectively, it means that the only case that would have compatibility issues is if the -class had a method named <code>__construct()</code> which was used for different semantics. + For backwards compatibility, if PHP 5 cannot find a <code>__construct()</code> + function for a given class, it will search for the old-style constructor function, + by the name of the class. Effectively, it means that the only case that would + have compatibility issues is if the class had a method named + <code>__construct()</code> which was used for different semantics. </p> <h2>Destructors</h2> <p> -Having the ability to define destructors for objects can be very useful. Destructors can log messages -for debugging, close database connections and do other clean-up work. No mechanism for object destructors -existed in PHP 4, although PHP had already support for registering functions which should be -run on request shutdown. + Having the ability to define destructors for objects can be very useful. + Destructors can log messages for debugging, close database connections and do + other clean-up work. No mechanism for object destructors existed in PHP 4, + although PHP had already support for registering functions which should be + run on request shutdown. </p> <p> -PHP 5 introduces a destructor concept similar to that of other object-oriented languages, such -as Java: When the last reference to an object is destroyed the object's destructor, which is a class method -name %__destruct()% that recieves no parameters, is called before the object is freed from memory. + PHP 5 introduces a destructor concept similar to that of other object-oriented + languages, such as Java: When the last reference to an object is destroyed the + object's destructor, which is a class method named <code>__destruct()</code> + that recieves no parameters, is called before the object is freed from memory. </p> <h3>Example</h3> <p> @@ -386,14 +400,14 @@ ?>'); ?> </p> <p> -Like constructors, parent destructors will not be called implicitly by the engine. In -order to run a parent destructor, one would have to explicitly call <code>parent::__destruct()</code> -in the destructor body. + Like constructors, parent destructors will not be called implicitly by the + engine. In order to run a parent destructor, one would have to explicitly + call <code>parent::__destruct()</code> in the destructor body. </p> <h2>Constants</h2> <p> -PHP 5 introduces per-class constants: + PHP 5 introduces per-class constants: </p> <p> <?php highlight_string('<?php @@ -405,8 +419,9 @@ ?>'); ?> </p> <p> -PHP 5 allows for expressions within constants, however, constants are evaluated at compile time, therefore -no constants can be declared that rely on runtime information. + PHP 5 allows for expressions within constants, however, constants are + evaluated at compile time, therefore no constants can be declared that + rely on runtime information. </p> <p> <?php highlight_string('<?php @@ -418,13 +433,14 @@ ?>'); ?> </p> <p> -Old code that has no user-defined classes or functions named 'const' will run without modifications. + Old code that has no user-defined classes or functions named 'const' + will run without modifications. </p> <h2>Exceptions</h2> <p> -PHP 4 had no exception handling. PHP 5 introduces a exception model similar to -that of other programming languages. + PHP 4 had no exception handling. PHP 5 introduces a exception model similar + to that of other programming languages. </p> <h3>Example</h3> <p> @@ -443,14 +459,15 @@ ?>'); ?> </p> <p> -Old code that has no user-defined classes or functions 'catch', 'throw' and 'try' will run -without modifications. + Old code that has no user-defined classes or functions 'catch', 'throw' + and 'try' will run without modifications. </p> <h2>Dereferencing objects returned from functions</h2> <p> -In PHP 4 it wasn't possible to dereference objects returned by functions and make further -method calls on those objects. With the advent of Zend Engine 2, the following is now possible: + In PHP 4 it wasn't possible to dereference objects returned by functions + and make further method calls on those objects. With the advent of Zend + Engine 2, the following is now possible: </p> <p> <?php highlight_string('<?php @@ -494,8 +511,8 @@ <h2>Static Methods</h2> <p> -PHP 5 introduces the 'static' keyword to declare a method static, thus -callable from outside the object context. + PHP 5 introduces the 'static' keyword to declare a method static, thus + callable from outside the object context. </p> <h3>Example</h3> <p> @@ -510,13 +527,15 @@ ?>'); ?> </p> <p> -The pseudo variable $this is not available inside a method that has been declared static. + The pseudo variable <code>$this</code> is not available inside a method + that has been declared static. </p> <h2>instanceof</h2> <p> -PHP 5 introduces the <code>instanceof</code> keyword, that allows you to ascertain whether -or not an object is an instance of a class, or extends a class, or implements an interface. + PHP 5 introduces the <code>instanceof</code> keyword, that allows you to + ascertain whether or not an object is an instance of a class, or extends + a class, or implements an interface. </p> <h3>Example</h3> <p> @@ -533,9 +552,10 @@ <h2>Static function variables</h2> <p> -Statics are now treated at compile-time which allows developers to assign variables to statics by -reference. This change also greatly improves their performance but means that indirect references to -statics will not work anymore. + Statics are now treated at compile-time which allows developers to assign + variables to statics by reference. This change also greatly improves their + performance but means that indirect references to statics will not work + anymore. </p> <h2>Parameters that are passed by reference to a function may now have default values</h2> @@ -552,9 +572,9 @@ <h2>__autoload()</h2> <p> -The <code>__autoload()</code> interceptor function will be automatically called when an undeclared class -is to be instantiated. The name of that class will be passed to the __autoload() interceptor function -as its only argument. + The <code>__autoload()</code> interceptor function will be automatically called + when an undeclared class is to be instantiated. The name of that class will be + passed to the <code>__autoload()</code> interceptor function as its only argument. </p> <h3>Example</h3> <p> @@ -569,8 +589,9 @@ <h2>Overloadable Method calls and Property accesses</h2> <p> -Both method calls and property accesses can be overloaded via the <code>__call()</code>, -<code>__get()</code> and <code>__set()</code> methods. + Both method calls and property accesses can be overloaded via the + <code>__call()</code>, <code>__get()</code> and <code>__set()</code> + methods. </p> <h3>Example: __get() and __set()</h3> <p>
Index: phpweb/zend-engine-2.php diff -u phpweb/zend-engine-2.php:1.11 phpweb/zend-engine-2.php:1.12 --- phpweb/zend-engine-2.php:1.11 Mon Jul 28 04:31:37 2003 +++ phpweb/zend-engine-2.php Sat Aug 2 10:25:00 2003 @@ -1,5 +1,5 @@ <?php -// $Id: zend-engine-2.php,v 1.11 2003/07/28 08:31:37 goba Exp $ +// $Id: zend-engine-2.php,v 1.12 2003/08/02 14:25:00 goba Exp $ $_SERVER['BASE_PAGE'] = 'zend-engine-2.php'; include_once $_SERVER['DOCUMENT_ROOT'] . '/include/prepend.inc'; commonHeader("Changes in PHP 5/Zend Engine 2.0"); @@ -7,33 +7,38 @@ <h1>Changes in PHP 5/Zend Engine 2.0</h1> -<p>[ <a href="http://www.nexen.net/interview/index.php?id=32" target="_blank">Disponible en français</a> ]</p> +<p> + [ <a href="http://www.nexen.net/interview/index.php?id=32" target="_blank">Disponible + en français</a> ] +</p> <h2>New Object Model.</h2> <p> -PHP's handling of objects has been completely rewritten, allowing for better performance and more -features. In previous versions of PHP, objects were handled like primitive types (for -instance integers and strings). The drawback of this method was that semantically the whole object -was copied when a variable was assigned, or pass as a parameter to a method. In the new approach, -objects are referenced by handle, and not by value (one can think of a handle as an object's -identifier). + PHP's handling of objects has been completely rewritten, allowing for better + performance and more features. In previous versions of PHP, objects were + handled like primitive types (for instance integers and strings). The drawback + of this method was that semantically the whole object was copied when a + variable was assigned, or pass as a parameter to a method. In the new approach, + objects are referenced by handle, and not by value (one can think of a handle + as an object's identifier). </p> <p> -Many PHP programmers aren't even aware of the copying quirks of the old object model and, therefore, -the majority of PHP applications will work out of the box, or with very few modifications. + Many PHP programmers aren't even aware of the copying quirks of the old object + model and, therefore, the majority of PHP applications will work out of the box, + or with very few modifications. </p> <h2>Private and Protected Members</h2> <p> -PHP 5 introduces private and protected member variables, they allow you to define the visibility of class -properties. + PHP 5 introduces private and protected member variables, they allow you to + define the visibility of class properties. </p> <h3>Example</h3> <p> -Protected member variables can be accessed in classes extending the class -they are declared in, whereas private member variables can only be accessed -by the class they belong to. + Protected member variables can be accessed in classes extending the class + they are declared in, whereas private member variables can only be accessed + by the class they belong to. </p> <p> <?php highlight_string('<?php @@ -76,7 +81,7 @@ <h2>Private and protected methods</h2> <p> -With PHP 5 (Zend Engine 2), private and protected methods are also introduced. + With PHP 5 (Zend Engine 2), private and protected methods are also introduced. </p> <h3>Example</h3> @@ -106,15 +111,15 @@ </p> <p> -Old code that has no user-defined classes or functions named "public," "protected" -or "private" should run without modifications. + Old code that has no user-defined classes or functions named "public", + "protected" or "private" should run without modifications. </p> <h2>Abstract Classes and Methods</h2> <p> -PHP 5 also introduces abstract classes and methods. An abstract method only declares the -method's signature and does not provide an implementation. A class that contains abstract -methods needs to be declared abstract. + PHP 5 also introduces abstract classes and methods. An abstract method + only declares the method's signature and does not provide an implementation. + A class that contains abstract methods needs to be declared abstract. </p> <h3>Example</h3> <p> @@ -135,15 +140,15 @@ </p> <p> -Abstract classes cannot be instantiated. Old code that has no user-defined classes or -functions named 'abstract' should run without modifications. + Abstract classes cannot be instantiated. Old code that has no user-defined + classes or functions named 'abstract' should run without modifications. </p> <h2>Interfaces</h2> <p> -The Zend Engine 2.0 introduces interfaces. A class may implement an arbitrary list -of interfaces. + The Zend Engine 2.0 introduces interfaces. A class may implement an arbitrary + list of interfaces. </p> <h3>Example</h3> @@ -161,14 +166,15 @@ </p> <p> -Old code that has no user-defined classes or functions named 'interface' or -'implements' should run without modifications. + Old code that has no user-defined classes or functions named 'interface' or + 'implements' should run without modifications. </p> <h2>Class Type Hints</h2> <p> -While remaining loosely typed PHP 5 introduces the ability to use class type hints to declare -the expected class of objects that are passed as parameters to a method. + While remaining loosely typed PHP 5 introduces the ability to use class type + hints to declare the expected class of objects that are passed as parameters + to a method. </p> <h3>Example</h3> <p> @@ -199,8 +205,8 @@ ?>'); ?> </p> <p> -These class type hints are not checked upon compilation, as would be the case -in a typed language, but during runtime. This means that: + These class type hints are not checked upon compilation, as would be the case + in a typed language, but during runtime. This means that: </p> <p> <?php @@ -212,7 +218,7 @@ ?> </p> <p> -is equivalent to: + is equivalent to: </p> <p> <?php @@ -225,13 +231,13 @@ ?>'); ?> </p> <p> -This syntax only applies to objects/classes, not built-in types. + This syntax only applies to objects/classes, not built-in types. </p> <h2>final</h2> <p> -PHP 5 introduces the "final" keyword to declare final members and methods. Methods and -members declared final cannot be overridden by sub-classes. + PHP 5 introduces the "final" keyword to declare final members and methods. + Methods and members declared final cannot be overridden by sub-classes. </p> <h3>Example</h3> <p> @@ -244,27 +250,28 @@ ?>'); ?> </p> <p> -Old code that has no user-defined classes or functions named 'final' should run -without modifications. + Old code that has no user-defined classes or functions named 'final' should + run without modifications. </p> <h2>Object Cloning</h2> <p> -PHP 4 (Zend Engine 1.0) offered no way a user could decide what copy constructor to run -when an object is duplicated. During duplication, PHP 4 did a bit for bit copy making an -identical replica of all the object's properties. -</p> -<p> -Creating a copy of an object with fully replicated properties is not always the wanted -behavior. A good example of the need for copy constructors, is if you have an object which -represents a GTK window and the object holds the resource of this GTK window, when you -create a duplicate you might want to create a new window with the same properties and have -the new object hold the resource of the new window. Another example is if your object holds -a reference to another object which it uses and when you replicate the parent object you want -to create a new instance of this other object so that the replica has its own separate copy. + PHP 4 (Zend Engine 1.0) offered no way a user could decide what copy constructor + to run when an object is duplicated. During duplication, PHP 4 did a bit for bit + copy making an identical replica of all the object's properties. +</p> +<p> + Creating a copy of an object with fully replicated properties is not always the + wanted behavior. A good example of the need for copy constructors, is if you have + an object which represents a GTK window and the object holds the resource of this + GTK window, when you create a duplicate you might want to create a new window with + the same properties and have the new object hold the resource of the new window. + Another example is if your object holds a reference to another object which it + uses and when you replicate the parent object you want to create a new instance + of this other object so that the replica has its own separate copy. </p> <p> -An object copy is created by calling the object's <code>__clone()</code> method: + An object copy is created by calling the object's <code>__clone()</code> method: </p> <p> <?php highlight_string('<?php @@ -272,13 +279,14 @@ ?>'); ?> </p> <p> -When the developer asks to create a new copy of an object, the Zend Engine will check if a -<code>__clone()</code> method has been defined or not. If not, it will call a default <code>__clone()</code> -which will copy all of the object's properties. If a <code>__clone()</code> method is defined, -then it will be responsible to set the necessary properties in the created object. For convenience, -the engine will supply a function that imports all of the properties from the source object, so -that they can start with a by-value replica of the source object, and only override properties that -need to be changed. + When the developer asks to create a new copy of an object, the Zend Engine will + check if a <code>__clone()</code> method has been defined or not. If not, it + will call a default <code>__clone()</code> which will copy all of the object's + properties. If a <code>__clone()</code> method is defined, then it will be + responsible to set the necessary properties in the created object. For + convenience, the engine will supply a function that imports all of the properties + from the source object, so that they can start with a by-value replica of the + source object, and only override properties that need to be changed. </p> <h3>Example</h3> <p> @@ -315,19 +323,22 @@ <h2>Unified Constructors</h2> <p> -The Zend Engine allows developers to declare constructor methods for classes. Classes -which have a constructor method call this method on each newly-created object, so it is -suitable for any initialization that the object may need before it is used. -</p> -<p> -With PHP 4, constructor methods were class methods that had the same name as the class itself. Since -it is very common to call parent constructors from derived classes, the way PHP 4 worked made it a bit -cumbersome to move classes around in a large class hierarchy. If a class is moved to reside under a -different parent, the constructor name of that parent changes as well, and the code in the derived class -that calls the parent constructor has to be modified. + The Zend Engine allows developers to declare constructor methods for classes. + Classes which have a constructor method call this method on each newly-created + object, so it is suitable for any initialization that the object may need + before it is used. +</p> +<p> + With PHP 4, constructor methods were class methods that had the same name as + the class itself. Since it is very common to call parent constructors from derived + classes, the way PHP 4 worked made it a bit cumbersome to move classes around + in a large class hierarchy. If a class is moved to reside under a different + parent, the constructor name of that parent changes as well, and the code in + the derived class that calls the parent constructor has to be modified. </p> <p> -PHP 5 introduces a standard way of declaring constructor methods by calling them by the name <code>__construct()</code>. + PHP 5 introduces a standard way of declaring constructor methods by calling + them by the name <code>__construct()</code>. </p> <h3>Example</h3> <p> @@ -350,23 +361,26 @@ ?>'); ?> </p> <p> -For backwards compatibility, if PHP 5 cannot find a <code>__construct()</code> function -for a given class, it will search for the old-style constructor function, by the name of the -class. Effectively, it means that the only case that would have compatibility issues is if the -class had a method named <code>__construct()</code> which was used for different semantics. + For backwards compatibility, if PHP 5 cannot find a <code>__construct()</code> + function for a given class, it will search for the old-style constructor function, + by the name of the class. Effectively, it means that the only case that would + have compatibility issues is if the class had a method named + <code>__construct()</code> which was used for different semantics. </p> <h2>Destructors</h2> <p> -Having the ability to define destructors for objects can be very useful. Destructors can log messages -for debugging, close database connections and do other clean-up work. No mechanism for object destructors -existed in PHP 4, although PHP had already support for registering functions which should be -run on request shutdown. + Having the ability to define destructors for objects can be very useful. + Destructors can log messages for debugging, close database connections and do + other clean-up work. No mechanism for object destructors existed in PHP 4, + although PHP had already support for registering functions which should be + run on request shutdown. </p> <p> -PHP 5 introduces a destructor concept similar to that of other object-oriented languages, such -as Java: When the last reference to an object is destroyed the object's destructor, which is a class method -name %__destruct()% that recieves no parameters, is called before the object is freed from memory. + PHP 5 introduces a destructor concept similar to that of other object-oriented + languages, such as Java: When the last reference to an object is destroyed the + object's destructor, which is a class method named <code>__destruct()</code> + that recieves no parameters, is called before the object is freed from memory. </p> <h3>Example</h3> <p> @@ -386,14 +400,14 @@ ?>'); ?> </p> <p> -Like constructors, parent destructors will not be called implicitly by the engine. In -order to run a parent destructor, one would have to explicitly call <code>parent::__destruct()</code> -in the destructor body. + Like constructors, parent destructors will not be called implicitly by the + engine. In order to run a parent destructor, one would have to explicitly + call <code>parent::__destruct()</code> in the destructor body. </p> <h2>Constants</h2> <p> -PHP 5 introduces per-class constants: + PHP 5 introduces per-class constants: </p> <p> <?php highlight_string('<?php @@ -405,8 +419,9 @@ ?>'); ?> </p> <p> -PHP 5 allows for expressions within constants, however, constants are evaluated at compile time, therefore -no constants can be declared that rely on runtime information. + PHP 5 allows for expressions within constants, however, constants are + evaluated at compile time, therefore no constants can be declared that + rely on runtime information. </p> <p> <?php highlight_string('<?php @@ -418,13 +433,14 @@ ?>'); ?> </p> <p> -Old code that has no user-defined classes or functions named 'const' will run without modifications. + Old code that has no user-defined classes or functions named 'const' + will run without modifications. </p> <h2>Exceptions</h2> <p> -PHP 4 had no exception handling. PHP 5 introduces a exception model similar to -that of other programming languages. + PHP 4 had no exception handling. PHP 5 introduces a exception model similar + to that of other programming languages. </p> <h3>Example</h3> <p> @@ -443,14 +459,15 @@ ?>'); ?> </p> <p> -Old code that has no user-defined classes or functions 'catch', 'throw' and 'try' will run -without modifications. + Old code that has no user-defined classes or functions 'catch', 'throw' + and 'try' will run without modifications. </p> <h2>Dereferencing objects returned from functions</h2> <p> -In PHP 4 it wasn't possible to dereference objects returned by functions and make further -method calls on those objects. With the advent of Zend Engine 2, the following is now possible: + In PHP 4 it wasn't possible to dereference objects returned by functions + and make further method calls on those objects. With the advent of Zend + Engine 2, the following is now possible: </p> <p> <?php highlight_string('<?php @@ -494,8 +511,8 @@ <h2>Static Methods</h2> <p> -PHP 5 introduces the 'static' keyword to declare a method static, thus -callable from outside the object context. + PHP 5 introduces the 'static' keyword to declare a method static, thus + callable from outside the object context. </p> <h3>Example</h3> <p> @@ -510,13 +527,15 @@ ?>'); ?> </p> <p> -The pseudo variable $this is not available inside a method that has been declared static. + The pseudo variable <code>$this</code> is not available inside a method + that has been declared static. </p> <h2>instanceof</h2> <p> -PHP 5 introduces the <code>instanceof</code> keyword, that allows you to ascertain whether -or not an object is an instance of a class, or extends a class, or implements an interface. + PHP 5 introduces the <code>instanceof</code> keyword, that allows you to + ascertain whether or not an object is an instance of a class, or extends + a class, or implements an interface. </p> <h3>Example</h3> <p> @@ -533,9 +552,10 @@ <h2>Static function variables</h2> <p> -Statics are now treated at compile-time which allows developers to assign variables to statics by -reference. This change also greatly improves their performance but means that indirect references to -statics will not work anymore. + Statics are now treated at compile-time which allows developers to assign + variables to statics by reference. This change also greatly improves their + performance but means that indirect references to statics will not work + anymore. </p> <h2>Parameters that are passed by reference to a function may now have default values</h2> @@ -552,9 +572,9 @@ <h2>__autoload()</h2> <p> -The <code>__autoload()</code> interceptor function will be automatically called when an undeclared class -is to be instantiated. The name of that class will be passed to the __autoload() interceptor function -as its only argument. + The <code>__autoload()</code> interceptor function will be automatically called + when an undeclared class is to be instantiated. The name of that class will be + passed to the <code>__autoload()</code> interceptor function as its only argument. </p> <h3>Example</h3> <p> @@ -569,8 +589,9 @@ <h2>Overloadable Method calls and Property accesses</h2> <p> -Both method calls and property accesses can be overloaded via the <code>__call()</code>, -<code>__get()</code> and <code>__set()</code> methods. + Both method calls and property accesses can be overloaded via the + <code>__call()</code>, <code>__get()</code> and <code>__set()</code> + methods. </p> <h3>Example: __get() and __set()</h3> <p>