<?php

function validaHoras($campo){
    return preg_match('/^(0[0-9]|1[0-9]|2[0-3]):([0-5][0-9])/', $campo) ? $campo : false;
}


$arr = array('00:00', '19:59', '20:34', '24:33', '22:64', '07:59', '000:30', '30:50', '99:99');

foreach($arr as $item) var_dump(validaHoras($item));