note 89078 modified in function.is-null by danbrown
| From: | danbrown@php.net | Date: | Fri, 20 Feb 2009 16:26:23 +0000 |
| Subject: | note 89078 modified in function.is-null by danbrown | ||
| References: | 1 | Groups: | php.notes |
| Request: | Send a blank email to php-notes+get-150898@lists.php.net to get a copy of this message | ||
If you want to test if a class is null or not, always use is_null($class) instead of "$class ==
null". If the class instance has no members, then "$class == null" will be true.
Here is an example:
<?php
class ClassA
{
function printSomething()
{
print('Something');
}
}
class ClassB
{
var $doNothing;
function ClassB()
{
$this->doNothing = 'Nothing';
}
function printSomething()
{
print('Something');
}
}
$a = new ClassA();
print('<br> #1: ' . ($a == null ? '$a is null' : '$a is not
null'));
print('<br> #2: ' . (is_null($a) ? '$a is null' : '$a is not
null'));
$b = new ClassB();
print('<br> #3: ' . ($b == null ? '$b is null' : '$b is not
null'));
print('<br> #4: ' . (is_null($b) ? '$b is null' : '$b is not
null'));
?>
The output of above is:
#1: $a is null
#2: $a is not null
#3: $b is not null
#4: $b is not null
--was--
If you want to test if a class is null or not, always use is_null($class) instead of "$class ==
null". If the class instance has no members, then "$class == null" will be true.
Here is an example:
class ClassA
{
function printSomething()
{
print('Something');
}
}
class ClassB
{
var $doNothing;
function ClassB()
{
$this->doNothing = 'Nothing';
}
function printSomething()
{
print('Something');
}
}
$a = new ClassA();
print('<br> #1: ' . ($a == null ? '$a is null' : '$a is not
null'));
print('<br> #2: ' . (is_null($a) ? '$a is null' : '$a is not
null'));
$b = new ClassB();
print('<br> #3: ' . ($b == null ? '$b is null' : '$b is not
null'));
print('<br> #4: ' . (is_null($b) ? '$b is null' : '$b is not
null'));
The output of above is:
#1: $a is null
#2: $a is not null
#3: $b is not null
#4: $b is not null
http://php.net/manual/en/function.is-null.php