Attributes, reflection and PHP

After a long exposure to .NET, when I get back to PHP I sometimes find myself missing some cool functionality (and a good IDE too… none of those I’ve tried so far can compete with the comfort of VisualStudio + ReSharper).

Among these missing features, attributes are what I needed in order to solve a certain problem in an elegant way.

Looking at what the reflection API was offering, I came up with a simple way to decorate my properties/methods/classes with attributes: through the documentation comments!

Let’s see an example:

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<pre>
<?

class A
{
/**
* @attr
* @attr2
*/
protected $foo;

protected function GetPropAttrs( $property )
{
$class = new ReflectionClass( get_class( $this ));
$prop = $class->getProperty( $property );
$doc = $prop->getDocComment();
$attrs = array();
$matches = array();

preg_match_all( '/@([a-zA-Z_][a-zA-Z_0-9]*)/m',
$doc, $matches, PREG_SET_ORDER );

foreach( $matches as $m )
$attrs[] = $m[ 1 ];

return( $attrs );
}

public function test()
{
$attrs = $this->GetPropAttrs( 'foo' );

print_r( $attrs );
}
}

class B
extends A
{
/**
* @attr3
*/
protected $foo;
}

$obj = new A();

print( 'Test A:<br>' );
$obj->test();

$obj = new B();

print( '<p>Test B:<br>' );
$obj->test();

?>
</pre>

Running the above script you’ll see the following output, confirming that everything works as desired:

Test A:
Array
(
    [0] => attr
    [1] => attr2
)

Test B:
Array ( [0] => attr3 )

If you’re using the /** */ comments for real documentation, you might want to use another escape character rather than @, to avoid problems.

Happy coding 🙂

Simone Tellini

Attributes, reflection and PHP

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