--TEST-- preg_replace() --FILE-- <?php var_dump(preg_replace('{{\D+}}', 'x', '{abcd}')); var_dump(preg_replace('{{\D+}}', 'ddd', 'abcd')); var_dump(preg_replace('/(ab)(c)(d)(e)(f)(g)(h)(i)(j)(k)/', 'a${1}2$103', 'zabcdefghijkl')); ?> --EXPECTF-- string(1) "x" string(4) "abcd" string(8) "zaab2k3l"