PHP - Manual: 类与对象

2024-12-21

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farzan at ifarzan dot com ¶

17 years ago


PHP 5 is very very flexible in accessing member variables and member functions. These access methods maybe look unusual and unnecessary at first glance; but they are very useful sometimes; specially when you work with SimpleXML classes and objects. I have posted a similar comment in SimpleXML function reference section, but this one is more comprehensive.


I use the following class as reference for all examples:


<?php

class Foo {

    public $aMemberVar = 'aMemberVar Member Variable';

    public $aFuncName = 'aMemberFunc';

    

    

    function aMemberFunc() {

        print 'Inside `aMemberFunc()`';

    }

}


$foo = new Foo;

?>



You can access member variables in an object using another variable as name:


<?php

$element = 'aMemberVar';

print $foo->$element; // prints "aMemberVar Member Variable"

?>



or use functions:


<?php

function getVarName()

{ return 'aMemberVar'; }


print $foo->{getVarName()}; // prints "aMemberVar Member Variable"

?>



Important Note: You must surround function name with { and } or PHP would think you are calling a member function of object "foo".


you can use a constant or literal as well:


<?php

define(MY_CONSTANT, 'aMemberVar');

print $foo->{MY_CONSTANT}; // Prints "aMemberVar Member Variable"

print $foo->{'aMemberVar'}; // Prints "aMemberVar Member Variable"

?>



You can use members of other objects as well:


<?php

print $foo->{$otherObj->var};

print $foo->{$otherObj->func()};

?>



You can use mathods above to access member functions as well:


<?php

print $foo->{'aMemberFunc'}(); // Prints "Inside `aMemberFunc()`"

print $foo->{$foo->aFuncName}(); // Prints "Inside `aMemberFunc()`"

?>

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