类与对象

farzan at ifarzan dot com ¶ 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()`"
?>