<?php

function validar_horas($hora) 
{
   return date('H:i', strtotime($hora)) == $hora;
}


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

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