ZEND PHP 5 Certification STUDY GUIDE

Object Oriented Programming in PHP ” 123
tion—that’s something you can only do within one of the class’ methods (typically,
the constructor).
Constants, Static Methods and Properties
Along with PPP, PHP 5 also implements static methods and properties. Unlike regular
methods and properties, their static counterparts exist and are accessible as part
of a class itself, as opposed to existing only within the scope of one of its instances.
This allows you to treat classes as true containers of interrelated functions and data
elements—which, in turn, is a very handy expedient to avoid naming conflicts.
While PHP 4 allowed you to call any method of a class statically using the scope
resolution operator :: (officially known as Paamayim Nekudotayim—Hebrew for
“Double Colon”), PHP 5 introduces a stricter syntax that calls for the use of the static
keyword to convey the use of properties and methods as such.
PHP is very strict about the use of static properties; calling static properties using
object notation (i.e. $obj->property) will result in both a “strict standards” message
and a notice. This is not the case with static methods, however calling a non-static
method statically will also emit a “strict standards” message.
class foo {
static $bar = "bat";
public static function baz()
{
echo "Hello World";
}
}
$foo = new foo();
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$foo->baz();
echo $foo->bar;
This example will display:
Hello WorldPHP Strict Standards: Accessing static property foo::$bar as non
static in PHPDocument1 on line 17