    <?php
     
    function Func_2($time){
       $hms = explode(":", $time);
       return $hms[0] + $hms[1]/60 + $hms[2]/3600;
    }
     
    function Func_1($dec){
       $s       = round($dec*3600);
       $hours   = floor($dec);
       $minutes = floor(($s%3600)/60);
       $seconds = $s%60;
       return sprintf('%02d:%02d:%02d', $hours, $minutes, $seconds);
    } 

    for ($teste = 7; $teste < 3600 * 7; $teste += 29) {
       $string  = Func_1($teste/3600);
       $decimal = Func_2($string);
       $extenso = Func_1($decimal);
       echo $string.'  |  '.$decimal.'  |  '.$extenso.PHP_EOL;
    }