How to find all classes used in a PHP file?

Question

How to find all classes used in a PHP file?

I'm trying to use a tokenizer to scan a file to find all the specific classes, everything that they extend, any instantiated instances, and anytime they were statically called.

<?php

$tokens = token_get_all(file_get_contents($file));

$used_classes = array();
$defined_classes = array();
$variable_classes = array();

foreach($tokens as $i => $token) {

    if(is_array($token)) {

        if(isset($tokens[$i - 2][0], $tokens[$i - 1][0])) {

            // new [class]
            if ($tokens[$i - 2][0] == T_NEW AND $tokens[$i - 1][0] == T_WHITESPACE) {

                if($tokens[$i][0] == T_STRING) {
                    $used_classes[$token[1]] = TRUE;

                // new $variable()
                } elseif($tokens[$i][0] == T_VARIABLE) {    

                    // @todo, this is really broken. However, do best to look for the assignment
                    if(preg_match('~\$var\s*=\s*([\'"])((?:(?!\1).)*)\1~', $text, $match)) {
                        if(empty($extension_classes[$match[2]])) {
                            $used_classes[$match[2]] = TRUE;
                        }
                    } elseif($token[1] !== '$this') {
                        $variable_classes[$token[1]] = TRUE;
                    }
                }

            }

            // class [class]
            if ($tokens[$i - 2][0] == T_CLASS AND $tokens[$i - 1][0] == T_WHITESPACE) {

                if($tokens[$i][0] == T_STRING) {
                    $defined_classes[$token[1]] = TRUE;
                }
            }


            // @todo: find more classes \/

            // class [classname] extends [class] ???
            // [class]::method()???
        }
    }
}