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    Michael Richey
    13 years ago
    Attempting various singleton base class methods described on this page, I have created a base class and bridge function that allows it to work without get_called_class() if it's not available. Unlike other methods listed here, I chose not to prevent use of __construct() or __clone().

    <?php
    abstract class Singleton {
    protected static     $m_pInstance;
    final public static function     getInstance(){
    $class = static::getClass();
    if(!isset(static::    $m_pInstance[$class])) {
    static::    $m_pInstance[$class] = new $class;
    }
    return static::    $m_pInstance[$class];
    }
    final public static function     getClass(){
    return     get_called_class();
    }
    }

    // I don't remember where I found this, but this is to allow php < 5.3 to use this method.
    if (!function_exists('get_called_class')) {
    function     get_called_class($bt = false, $l = 1) {
    if (!    $bt)
    $bt = debug_backtrace();
    if (!isset(    $bt[$l]))
    throw new     Exception("Cannot find called class -> stack level too deep.");
    if (!isset(    $bt[$l]['type'])) {
    throw new     Exception('type not set');
    }
    else
    switch (    $bt[$l]['type']) {
    case     '::':
    $lines = file($bt[$l]['file']);
    $i = 0;
    $callerLine = '';
    do {
    $i++;
    $callerLine = $lines[$bt[$l]['line'] - $i] . $callerLine;
    } while (    stripos($callerLine, $bt[$l]['function']) === false);
    preg_match('/([a-zA-Z0-9\_]+)::' . $bt[$l]['function'] . '/', $callerLine, $matches);
    if (!isset(    $matches[1])) {
    // must be an edge case.
    throw new Exception("Could not find caller class: originating method call is obscured.");
    }
    switch (    $matches[1]) {
    case     'self':
    case     'parent':
    return     get_called_class($bt, $l + 1);
    default:
    return     $matches[1];
    }
    // won't get here.
    case '->': switch ($bt[$l]['function']) {
    case     '__get':
    // edge case -> get class of calling object
    if (!is_object($bt[$l]['object']))
    throw new     Exception("Edge case fail. __get called on non object.");
    return     get_class($bt[$l]['object']);
    default: return     $bt[$l]['class'];
    }

    default: throw new     Exception("Unknown backtrace method type");
    }
    }
    }

    class     B extends Singleton {
    }

    class     C extends Singleton {
    }

    $b = B::getInstance();
    echo     'class: '.get_class($b);

    echo     '<br />';

    $c = C::getInstance();
    echo echo     'class: '.get_class($c);
    ?>
    This returns:
    class: b
    class: c

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