Time or Time interval conversion with PHP

Question

i have the below given time interval options in a dropdown (those are strings)

<select name="CSSAtapsClient[client_time_window][0]" id="client_time_window_0">
<option value="5702">7am - 10am</option>
<option value="5703">10am - 1pm</option>
<option value="5704">12pm - 3pm</option>
<option value="5705">3pm - 6pm</option>
<option value="5706">6pm - 9pm</option>
<option value="5707">7pm - 10pm</option>
<option value="5708">9pm - 12am</option>
<option value="5709">12am - 7am</option>
</select>

I need to convert these intervals for a specific GMT time zone. for example lets say its in GMT +8 and i need to convert it to GMT +10 and it can be done by adding 2 hours.

so if the given time interval is, 7am - 10am (GMT +8) it should come as 9am - 12pm (GMT +10)

What is the best way to convert this kind of a time interval ? The issue i am seeing here is its a string (time interval).

Appreciate an early reply.

EDIT 1

I am converting to only Australian states so there is no chance of getting a day as difference when converting. pls check this link http://www.timebie.com/tz/australiatimezone.php

Answer 1

My completed answer.

<?php

function is_am_pm($str) {
   if (strpos($str, "am") !== false || strpos($str, "AM") !== false)
      return "am";
   if (strpos($str, "pm") !== false || strpos($str, "PM") !== false)
      return "pm";
}

function get_only_int($str) {
   if (strpos($str, ".") !== false) {
      if (preg_match_all("/\s(.*?)\.(.*?)$/", $str, $matches))
         return trim(trim($matches[0][0]), "+");
   }else {
      return (int) preg_replace('/\D/', '', $str);
   }
}

function gmt_to_gmt($str, $from_gmt, $to_gmt = "GMT +10") {
   if (!is_numeric($from_gmt))
      $from_gmt = get_only_int($from_gmt);
   if (!is_numeric($to_gmt))
      $to_gmt = get_only_int($to_gmt);

   $temp_time = explode("-", $str);

   $begin_time_s = is_am_pm($temp_time[0]);
   $begin_time = get_only_int(trim($temp_time[0]));
   $end_time_s = is_am_pm($temp_time[1]);
   $end_time = get_only_int(trim($temp_time[1]));


   $time_diff = $to_gmt - $from_gmt;
   $begin_time = $begin_time + $time_diff;
   $end_time = $end_time + $time_diff;

   if ($begin_time > 11.59) {
      if ($begin_time_s == "am") {
         $begin_time >= 12 && $begin_time < 13 ? $begin_time : $begin_time -= 12; // 13.3 - 12
         $begin_time .= "pm";
      } else {
         $begin_time >= 12 && $begin_time < 13 ? $begin_time : $begin_time -= 12;
         $begin_time .= "am";
      }
   } else {
      $begin_time .= $begin_time_s;
   }

   if ($end_time > 11.59) { // 11.3
      if ($end_time_s == "am") {
         $end_time >= 12 && $end_time < 13 ? $end_time : $end_time -= 12;
         $end_time .= "pm";
      } else {
         $end_time >= 12 && $end_time < 13 ? $end_time : $end_time -= 12;
         $end_time .= "am";
      }
   } else {
      $end_time .= $end_time_s;
   }

   return format_string($begin_time)." - ".format_string($end_time);
}

function format_string($str) {
   $temp_am_pm = is_am_pm($str);
   $str = (float) preg_replace('/^\D*/', '', $str);
   $val = '';

   if (is_int($str))
      $val = sprintf("%02s", $str);

   else if (is_float($str))
      $val = str_pad(sprintf("%0.2f", $str), 5, '0', STR_PAD_LEFT);

   return $val.$temp_am_pm;
}
echo gmt_to_gmt("12am - 1pm", "GMT +0", "GMT +2.30");

?>

Output - 02.30pm - 03.30pm

Answer 2

Try this functions. (Based on your edit i made $to_gmt var of my gmt_to_gmt function default value is "GMT +10")

    <?php

        function is_am_pm($str){
            if(strpos($str, "am") !== false || strpos($str, "AM") !== false) return "am";
            if(strpos($str, "pm") !== false || strpos($str, "PM") !== false) return "pm";
        }
        function get_only_int($str){
            if(strpos($str, ".") !== false){
                if(preg_match_all("/\s(.*?)\.(.*?)$/", $str, $matches))
                    return trim(trim($matches[0][0]),"+");

            }else{
                return (int) preg_replace('/\D/', '', $str);
            }
        }
        function gmt_to_gmt($str,$from_gmt,$to_gmt = "GMT +10"){
            if(!is_numeric($from_gmt)) $from_gmt = get_only_int($from_gmt);
            if(!is_numeric($to_gmt)) $to_gmt = get_only_int($to_gmt);

            $temp_time = explode("-",$str);

            $begin_time_s   = is_am_pm($temp_time[0]);
            $begin_time     = get_only_int(trim($temp_time[0]));
            $end_time_s     = is_am_pm($temp_time[1]);
            $end_time       = get_only_int(trim($temp_time[1]));


            $time_diff  = $to_gmt - $from_gmt;

            $begin_time = $begin_time + $time_diff;
            $end_time   = $end_time + $time_diff;

            if($begin_time > 11){
                if($begin_time_s == "am"){
                    $begin_time >= 12 && $begin_time < 13 ? $begin_time : $begin_time -= 12;
                    $begin_time .= "pm";  
                }else{
                    $begin_time >= 12 && $begin_time < 13 ? $begin_time : $begin_time -= 12;
                    $begin_time .= "am";  
                }
            }else{
                $begin_time .= $begin_time_s;
            }

            if($end_time > 11){

                if($end_time_s == "am"){
                    $end_time >= 12 && $end_time < 13 ? $end_time : $end_time -= 12;
                    $end_time .= "pm";  
                }else{
                    $end_time >= 12 && $end_time < 13 ? $end_time : $end_time -= 12;
                    $end_time .= "am";  
                }
            }else{

                $end_time .= $end_time_s;
            }

            return $begin_time . " - " . $end_time;
        }
        echo gmt_to_gmt("11am - 10pm", "GMT +0" , "GMT +2.5"); 
    ?>

Have a nice day