PHP: 类与对象

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:

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:

$element = 'aMemberVar';
print $foo->$element; // prints 'aMemberVar Member Variable'
?>

or use functions:

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:

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:

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

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

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