cvs: phpweb / zend-engine-2.php

goba Thu Oct 30 15:01:43 2003 EDT Modified files: /phpweb zend-engine-2.php Log: Fixing some small typos, and adding the new info available in ZEND_CHANGES_PHP_5_0_0b2.txt committed by Andi. As discussed, we will replace that txt with this file...

Index: phpweb/zend-engine-2.php diff -u phpweb/zend-engine-2.php:1.17 phpweb/zend-engine-2.php:1.18 --- phpweb/zend-engine-2.php:1.17 Fri Aug 8 09:08:18 2003 +++ phpweb/zend-engine-2.php Thu Oct 30 15:01:41 2003 @@ -1,5 +1,5 @@ <?php -// $Id: zend-engine-2.php,v 1.17 2003/08/08 13:08:18 goba Exp $ +// $Id: zend-engine-2.php,v 1.18 2003/10/30 20:01:41 goba Exp $ $_SERVER['BASE_PAGE'] = 'zend-engine-2.php'; include_once $_SERVER['DOCUMENT_ROOT'] . '/include/prepend.inc'; site_header("Changes in PHP 5/Zend Engine 2.0"); @@ -78,7 +78,7 @@ <h2>Private and protected methods</h2> <p> - With PHP 5 (Zend Engine 2), private and protected methods are also introduced. + With PHP 5, private and protected methods are also introduced. </p> <h3>Example</h3> <?php highlight_php('<?php @@ -136,7 +136,7 @@ <h2>Interfaces</h2> <p> - The Zend Engine 2.0 introduces interfaces. A class may implement an arbitrary + PHP 5 introduces interfaces. A class may implement an arbitrary list of interfaces. </p> <h3>Example</h3> @@ -147,7 +147,8 @@ class Exception implements Throwable { public function getMessage() { - // ... + // ... + } } ?>'); ?> <p> @@ -227,15 +228,33 @@ } ?>'); ?> <p> + It is furthermore possible to make a class final. Doing this + prevents a class from being specialized (it cannot be inherited + by another class). There's no need to declare the methods of + a final class themselves as final. +</p> +<h3>Example</h3> +<?php highlight_php('<?php +final class Foo { + // class definition +} + +// the next line is impossible +// class Bork extends Foo {} +?>'); ?> +<p> + Properties cannot be final. +</p> +<p> 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. + PHP 4 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 @@ -254,7 +273,7 @@ $copy_of_object = $object->__clone(); ?>'); ?> <p> - When the developer asks to create a new copy of an object, the Zend Engine will + When the developer asks to create a new copy of an object, PHP 5 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 @@ -296,7 +315,7 @@ <h2>Unified Constructors</h2> <p> - The Zend Engine allows developers to declare constructor methods for classes. + PHP 5 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. @@ -316,15 +335,15 @@ <h3>Example</h3> <?php highlight_php('<?php class BaseClass { - function __construct() { - print "In BaseClass constructor\n"; - } + function __construct() { + print "In BaseClass constructor\n"; + } } class SubClass extends BaseClass { - function __construct() { - parent::__construct(); - print "In SubClass constructor\n"; + function __construct() { + parent::__construct(); + print "In SubClass constructor\n"; } } @@ -356,13 +375,13 @@ <h3>Example</h3> <?php highlight_php('<?php class MyDestructableClass { - function __construct() { - print "In constructor\n"; + function __construct() { + print "In constructor\n"; $this->name = "MyDestructableClass"; } function __destruct() { - print "Destroying " . $this->name . "\n"; + print "Destroying " . $this->name . "\n"; } } @@ -380,7 +399,7 @@ </p> <?php highlight_php('<?php class Foo { - const constant = "constant"; + const constant = "constant"; } echo "Foo::constant = " . Foo::constant . "\n"; @@ -392,8 +411,8 @@ </p> <?php highlight_php('<?php class Bar { - const a = 1<<0; - const b = 1<<1; + const a = 1<<0; + const b = 1<<1; const c = a | b; } ?>'); ?> @@ -405,23 +424,121 @@ <h2>Exceptions</h2> <p> PHP 4 had no exception handling. PHP 5 introduces a exception model similar - to that of other programming languages. + to that of other programming languages. Note that there is support for "catch + all" and for the "finally" clause. +</p> +<p> + Exceptions can be rethrown in catch blocks. Also it is possible to + have multiple catch blocks. In that case the caught exception is + compared with the classtype of each catch block from top to bottom + and the first block that has an 'instanceof' match gets executed. + When the catch block finishes, execution continues at the end of + the last catch block. If no catch block has an 'instanceof' match + then the next try/catch block is searched until no more try/catch + blocks are available. In that case the exception is an uncaught + exception and the program terminates with showing the exception. </p> <h3>Example</h3> <?php highlight_php('<?php -class MyExceptionFoo extends Exception { +class MyException { + function __construct($exception) { + $this->exception = $exception; + } + + function Display() { + print "MyException: $this->exception\n"; + } +} + +class MyExceptionFoo extends MyException { function __construct($exception) { - parent::__construct($exception); + $this->exception = $exception; + } + + function Display() { + print "MyException: $this->exception\n"; } } try { - throw new MyExceptionFoo("Hello"); -} catch (MyExceptionFoo $exception) { - print $exception->getMessage(); + throw new MyExceptionFoo(\'Hello\'); +} +catch (MyException $exception) { + $exception->Display(); +} +catch (Exception $exception) { + echo $exception; +} +?>'); ?> +<p> + Even though the above example shows that it is possible to define + exception classes that don't inherit from Exception it is best to + do so. This is because the internal Exception class can gather a + lot of information otherwise not available. The PHP code emulation + code would look something like shown below. The comments show the + meaning of each property and hence their getter methods. As the code + shows it is possible to read any available information by using the + getter methods. But since some of the methods are used internally + they are marked final. All in all the class is very restrictive + because it must be ensured that anything used internally always + works as expected. +</p> +<h3>Example</h3> +<?php highlight_php('<?php +class Exception { + function __construct(string $message=NULL, int code=0) { + if (func_num_args()) { + $this->message = $message; + } + $this->code = $code; + $this->file = __FILE__; // of throw clause + $this->line = __LINE__; // of throw clause + $this->trace = debug_backtrace(); + $this->string = StringFormat($this); + } + + protected $message = \'Unknown exception\'; // exception message + protected $code = 0; // user defined exception code + protected $file; // source filename of exception + protected $line; // source line of exception + + private $trace; // backtrace of exception + private $string; // internal only!! + + final function getMessage() { + return $this->message; + } + final function getCode() { + return $this->code; + } + final function getFile() { + return $this->file; + } + final function getTrace() { + return $this->trace; + } + final function getTraceAsString() { + return self::TraceFormat($this); + } + function _toString() { + return $this->string; + } + static private function StringFormat(Exception $exception) { + // ... a function not available in PHP scripts + // that returns all relevant information as a string + } + static private function TraceFormat(Exception $exception) { + // ... a function not available in PHP scripts + // that returns the backtrace as a string + } } ?>'); ?> <p> + If you derive your exception classes from this Exception base class + your exceptions will be nicely shown in the builtin handler for + uncaught exceptions. +</p> +<p> Old code that has no user-defined classes or functions 'catch', 'throw' and 'try' will run without modifications. </p> @@ -429,8 +546,8 @@ <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: + and make further method calls on those objects. With PHP 5, the following + is now possible: </p> <?php highlight_php('<?php class Circle { @@ -463,9 +580,12 @@ <?php highlight_php('<?php class foo { static $my_static = 5; + public $my_prop = \'bla\'; } print foo::$my_static; +$obj = new foo; +print $obj->my_prop; ?>'); ?> <h2>Static Methods</h2> @@ -597,5 +717,179 @@ $a = $foo->test(1, "2", 3.4, true); var_dump($a); ?>'); ?> + +<h2>Iteration</h2> +<p> + Objects may be iterated in an overloaded way when used with + foreach. The default behavior is to iterate over all properties. +</p> +<h3>Example</h3> +<?php highlight_php('<?php +class Foo { + var $x = 1; + var $y = 2; +} + +$obj = new Foo; + +foreach ($obj as $prp_name => $prop_value) { + // using the property +} +?>'); ?> +<p> + Each class whose instances can be iterated with foreach should + implement the empty interface <code>Traversable</code>. Hence any object + that says it implements <code>Traversable</code> can be used with foreach. +</p> +<p> + The interfaces <code>IteratorAggregate</code> and <code>Iterator</code> + allows you to specify how class objects are iterated in PHP code. The first + of them simply has a method <code>getIterator()</code> which must return + an array or an object that either implements the interface <code>Iterator</code> + or is instantiated from an internal class that can be iterated. +</p> +<h3>Example</h3> +<?php highlight_php('<?php +class ObjectIterator implements Iterator { + + private $obj; + private $num; + + function __construct($obj) { + $this->obj = $obj; + } + function rewind() { + $this->num = 0; + } + function hasMore() { + return $this->num < $this->obj->max; + } + function key() { + return $this->num; + } + function current() { + switch($this->num) { + case 0: return "1st"; + case 1: return "2nd"; + case 2: return "3rd"; + default: return $this->num."th"; + } + } + function next() { + $this->num++; + } +} + +class Object implements IteratorAggregate { + + public $max = 3; + + function getIterator() { + return new ObjectIterator($this); + } +} + +$obj = new Object; + +// this foreach ... +foreach($obj as $key => $val) { + echo "$key = $val\n"; +} + +// matches the following 7 lines with the for directive. +$it = $obj->getIterator(); +for($it->rewind(); $it->hasMore(); $it->next) { + $key = $it->current(); + $val = $it->key(); + echo "$key = $val\n"; +} +unset($it); +?>'); ?> +<p> + The matching for directive is very intersting here since it shows + the use of all abstract methods declared in the interfaces + <code>Iterator</code> and <code>IteratorAggregate</code> respectively. +</p> + +<h2>New <code>__METHOD__</code> constant</h2> +<p> + The new <code>__METHOD__</code> pseudo constant shows the current class + and method when used inside a method and the function when used outside of a + class. +</p> +<h3>Example</h3> +<?php highlight_php('<?php +class Foo { + function Show() { + echo __FILE__ . \'(\' . __LINE__ . \')\' . __METHOD__; + } +} +function Test() { + echo __FILE__ . \'(\' . __LINE__ . \')\' . __METHOD__; +} +?>'); ?> + +<h2>New <code>__toString()</code> method</h2> + +<p> + The new <code>__toString()</code> magic method allows you to overload the + object to string conversion. +</p> +<h3>Example</h3> +<?php highlight_php('<?php +class Foo { + function __toString() { + return "What ever"; + } +} + +$obj = Foo; + +$str = (string) $obj; // call __toString() + +echo $obj; // call __toString() +?>'); ?> + +<h2>Reflection API</h2> + +<p> + PHP 5 comes with a complete reflection API that adds the ability to + reverse-engineer classes, interfaces, functions and methods as well + as extensions. +</p> + +<p> + The reflection API also offers ways of getting doc comments for + functions, classes and methods. +</p> + +<p> + Nearly all aspects of object oriented code can be reflected by + using the reflection API which is + <a href="http://sitten-polizei.de/php/reflection_api/docs/language.reflection.html">documented + separatley</a>. +</p> + +<h3>Example</h3> +<?php highlight_php('<?php +class Foo { + public $prop; + function Func($name) { + echo "Hello $name"; +} + +reflection_class::export(\'Foo\'); +reflection_object::export(new Foo); +reflection_method::export(\'Foo\', \'func\'); +reflection_property::export(\'Foo\', \'prop\'); +reflection_extension::export(\'standard\'); +?>'); ?> + +<h2>New memory manager</h2> +<p> + PHP 5 has a new memory manager which allows it to run efficiently in + multi-threaded environments as it doesn't need to use mutexes to lock + and unlock during allocation/deallocation. +</p> <?php site_footer(); ?>