$re = '/\B@\w+\(\'[\w+\s]+\',\s+
(?(?=\'(?=(\w+\)|\w+\()))
\'[\w\)\(]+\'
|(\'\w+\'|\$\w+)
)\)/x';
$str = '@extends(\'template\', \'te)st\')
@extends(\'template\', \'te())st\')
@extends(\'template\', \'te()st\')
@extends(\'template\', \'test\')
@extends(\'template\', \'te(st\')
@extends(\'template\', $test)
@extends(\'template\', test)
@extends(\'template\', \'test)';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php