Is there a way to find out how many times a class has been instantiated in php?

I'm currently using this method:

class Foo {
    private static $num_instances = 0;

    function __construct() {
        self::$num_instances++;
    }
}

which seems to work, but I'm wondering if there's a b开发者_如何学Pythonuilt in way....

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I would be surprised if there is one..
In my opinion it would be an overhead, if it is always counting the amount of created instances.

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You could use xdebug using the execution trace.

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You can always check $GLOBALS and count the number of class instantiations.

It wouldn't be pretty, and I would prefer to do it with a static property.

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One way to go about it could be to count the instances in the $GLOBALS (as suggested by Alix):

function count_instances( $class_name ) {
    $i = 0;
    foreach ( $GLOBALS as $key => $global ) {
        if ( 'global' === $key ) continue;
        if ( 'object' === gettype($global) ) {
            if ( $class_name === get_class($global) ) $i++;
        }
    }
    return $i;
}

But note that this would not include classes instantiated without being stored in a variable. For example, it will add the instance of $var = new className(); to $GLOBALS but not simply new className(); (just the call alone without encapsulation).