php后向引用怎么带入到函数参数

preg_replace('/{get_(\w+)}/',$arr[$1], $content);

$content = '{get_abc}';$arr['abc'] = 123;echo preg_replace('/{get_(\w+)}/e', '$arr["$1"]', $content);

$content = '{get_abc}';$arr['abc'] = 123;echo preg_replace_callback('/{get_(\w+)}/', 'back', $content);function back($m) {  global $arr;  return $arr[$m[1]];}

$content = '{get_abc}';$arr['abc'] = 123;echo preg_replace_callback('/{get_(\w+)}/', create_function('$m', 'global $arr; return $arr["$m[1]"];'), $content);

$content = '{get_abc}';$arr['abc'] = 123;echo preg_replace_callback('/{get_(\w+)}/', function($m) use($arr) { return $arr["$m[1]"];}, $content);