Converting To And From Decimal Time In PHP

Hi Philip,

Your code indeed works in the manner you have described, however there are a couple of finer details that caused issues for me when using the code.

In the time_to_decimal function, line 12 should read as follows:

$decTime = ($timeArr[0]*60) + ($timeArr[1]) + ($timeArr[2]/60);

As it is written in your post, the seconds are actually representing fractions of an hour (1/3600th) as opposed to fractions of a minute (1/60th). 

We have the same issue in the decimal_to_time function as well as an issue in regards to the round() function.  I've corrected the decimal_to_time function as follows:

function decimal_to_time($decimal) {
    $hours = floor((int)$decimal / 60);
    $minutes = floor((int)$decimal % 60);
    $seconds = $decimal - (int)$decimal; 
    $seconds = round($seconds * 60); 
 
    return str_pad($hours, 2, "0", STR_PAD_LEFT) . ":" . str_pad($minutes, 2, "0", STR_PAD_LEFT) . ":" . str_pad($seconds, 2, "0", STR_PAD_LEFT);
}

round() in lines 2 and 3 have been replaced by floor().  This is due to the behavior of round() returning 1 when given .5.  An example is as follows:

Say we are converting 1:30:30 into a decimal representing minutes.  Using the two functions posted we would have

echo time_to_decimal('1:30:30'); // prints 90.008333333333, seconds are still converted incorrectly

// this should display the input from the first function
echo decimal_to_time(90.008333333333); // prints 02:02:30, not correct

In the example, line 2 of the original code calculates to - round( 90 / 60 ) = round(1.5) = 2.  Since we only want the numer of whole hours in the $decimal variable, we should use floor() instead.  floor() will always round to the lowest whole number ( 1 in this case )

I hope this helps someone out there :)

hi tae, thanks..

i propose to change little to allow this kind of input "01:05" =1h05 or "01:05:00" or "01"=1hour

function time_to_decimal($time) {
  $timeArr = explode(':', $time);
  if (count($timeArr) == 3) {
    $decTime = ($timeArr[0]*60) + ($timeArr[1]) + ($timeArr[2]/60);
  } else if (count($timeArr) == 2) {
    $decTime = ($timeArr[0]) + ($timeArr[1]/60);
  } else if (count($timeArr) == 2) {
    $decTime = $time;
  }
  return $decTime;
}

This function kept returning :60 in the seconds place! I added :

if ($seconds == 60) {
   $minutes++; $seconds=0;
}

to the end of the function.

My 2 cents comment if used your function and added a format control to avoid strange behavior and surprise

function Time_To_Decimal($time) {
  $decTime = 0;
  if (preg_match("/^([01][0-9]|2[0-3]):([0-5][0-9]):([0-5][0-9])$/", $time, $matches)) {
    $decTime = ($matches[0]*60) + ($matches[1]) + ($matches[2]/60);
  }
  return $decTime;
}

Thanks a lot for posting

Sorry posted too quickly (fixed preg_match return array)

function Time_To_Decimal($time) {
  $decTime = 0;
  if (preg_match("/^([01][0-9]|2[0-3]):([0-5][0-9]):([0-5][0-9])$/", $time, $matches)) {
    $decTime = ($matches[1]*60) + ($matches[2]) + ($matches[3]/60);
  }
  return $decTime;
}

Error here

floor($decimal % 60);

and not

floor($decimal % / 60);