<?php
function pareceHora($str) {
&& $str[2] == ':'
&& $str[0] >= '0' && $str[0] <= '2'
&& $str[1] >= '0' && $str[1] <= ($str[0]=='2'?'3':'9')
&& $str[3] >= '0' && $str[3] <= '5'
&& $str[4] >= '0' && $str[4] <= '9';
}
echo pareceHora('00:12')?'S':'N';
echo pareceHora('22:50')?'S':'N';
echo pareceHora('12345')?'S':'N';
echo pareceHora('24:28')?'S':'N';
echo pareceHora('99:99')?'S':'N';
echo pareceHora('12:301')?'S':'N';
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