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Output Previous Weekday from Input Like "030507" (March 5, 2007)

Posted on 2007-03-23
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Last Modified: 2008-03-06
How to output the previous weekday?  
     If user inputs "030507" (Monday, March 5, 2007), I want to output "030207" (Friday, March 2, 2007), skipping back past Sunday and Saturday.  
     But if the user inputs "030607" (Tuesday, March 6, 2007), I want to output "030507" (Monday, March 5, 2007).
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Question by:Randall-B
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9 Comments
 
LVL 24

Accepted Solution

by:
glcummins earned 1000 total points
ID: 18782664
<?php

$input = "030507";

$inputMonth = substr($input, 0, 2);
$inputDay = substr($input, 2, 2);
$inputYear = substr($input, 4, 2);

$timestamp = mktime(0, 0, 0, $inputMonth, $inputDay, $inputYear);

getPreviousWeekday($timestamp);

function getPreviousWeekday($timestamp)
{
        // This function is called recursively until a weekday is found
      $previousDay = $timestamp - 86400; // Substract one day of seconds (24 hours x 60 minutes x 60 seconds)
      if (6 > date('N', $previousDay))
      {
            
            $previousWeekday = date('mdy', $previousDay);
            print "$previousWeekday<br />";
      }
      else
      {
            getPreviousWeekday($previousDay);
      }
}

?>
0
 

Author Comment

by:Randall-B
ID: 18782962
Great.  It works fine as a stand-alone script.  But then I combined it with another (which may look familiar to you), so it will echo each weekday of a given month, and also the previous weekday.
  In that situation it gives this error: Fatal error: Call to undefined function getpreviousweekday() .   Here is the complete script that I'm testing:

<?php

$inputDate = "March, 2007";

list($inputMonth, $inputYear) = explode(', ', $inputDate);

$daysInMonth = date('t', strtotime("$inputMonth $inputYear"));

for ($i=1; $i<=$daysInMonth; $i++)
{
      if (6 > date('N', strtotime("$i $inputMonth $inputYear")))
      {
         $weekday = date('mdy', strtotime("$i $inputMonth $inputYear"));

    ////////////  Get previous weekday /////////

            $inputMonth = substr($weekday, 0, 2);
            $inputDay = substr($weekday, 2, 2);
            $inputYear = substr($weekday, 4, 2);

           $timestamp = mktime(0, 0, 0, $inputMonth, $inputDay, $inputYear);

           getPreviousWeekday($timestamp);

           function getPreviousWeekday($timestamp) {
        // This function is called recursively until a weekday is found
           $previousDay = $timestamp - 86400; // Substract one day of seconds (24 hours x 60 minutes x 60 seconds)
             
                   if (6 > date('N', $previousDay)) {
           
                $previousWeekday = date('mdy', $previousDay);
                print "$previousWeekday<br />";
            } else {
               getPreviousWeekday($previousDay);
           }
        }
                  
       /////// END of get previous weekday //////////


          echo "<tr><td>$weekday $previousweekday</td></tr>";
      }
}
?>
0
 
LVL 24

Expert Comment

by:glcummins
ID: 18783013
You are defining the function 'getPreviousWeekday' within your for() loop, which will cause errors.

Take the entire 'getPreviousWeekday()' function and put it outside your loop:

<?php

$inputDate = "March, 2007";

list($inputMonth, $inputYear) = explode(', ', $inputDate);

$daysInMonth = date('t', strtotime("$inputMonth $inputYear"));

for ($i=1; $i<=$daysInMonth; $i++)
{
      if (6 > date('N', strtotime("$i $inputMonth $inputYear")))
      {
         $weekday = date('mdy', strtotime("$i $inputMonth $inputYear"));

    ////////////  Get previous weekday /////////

            $inputMonth = substr($weekday, 0, 2);
            $inputDay = substr($weekday, 2, 2);
            $inputYear = substr($weekday, 4, 2);

           $timestamp = mktime(0, 0, 0, $inputMonth, $inputDay, $inputYear);

           getPreviousWeekday($timestamp);

                 
       /////// END of get previous weekday //////////


          echo "<tr><td>$weekday $previousweekday</td></tr>";
      }
}

function getPreviousWeekday($timestamp) {
      // This function is called recursively until a weekday is found
      $previousDay = $timestamp - 86400; // Substract one day of seconds (24 hours x 60 minutes x 60 seconds)
      
            if (6 > date('N', $previousDay)) {
      
      $previousWeekday = date('mdy', $previousDay);
      print "$previousWeekday<br />";
      } else {
      getPreviousWeekday($previousDay);
      }
}
?>
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Author Comment

by:Randall-B
ID: 18783145
OK, that gets rid of that error, but now I get another error.
    I want to do:
 echo "<tr><td>$weekday $previousWeekday</td></tr>";

So I removed the echo $previousWeekday line from the function, and am trying to echo $previousWeekay in the table cell along with $weekday.  However, only one date is showing, and it is the unix timestamp error.

I want to get this:
   030107    022807
   030207    030107
   030507    030207
. . .  etc.

   But this is the output:

030107  
123169  
123169  
. . .  etc.
0
 
LVL 24

Expert Comment

by:glcummins
ID: 18783174
How about, add the print statement back into the getPreviousWeekday() function, and use this:

echo "<tr><td>$weekday ";
getPreviousWeekday($weekday);
echo "</td></tr>";

If that does not work, can you post your code as it stands now?
0
 

Author Comment

by:Randall-B
ID: 18783264
OK, that made it print two numbers, but not the right ones.  It's like this:

030107   123169
123169   010170
123169   010170
123169   010170
. . . etc.
   So I'm posting the code as it stood in my previous comment.  See:  http://216.92.61.99/weekdayphp.txt

But instead of the timestamp-based function, what about using something like this within the original loop, to simply detect if $weekday is a Monday, and if so, subtract 3 days to make it a Friday (but subtract only 1 day from the other weekdays):

if ((date('w'), $weekday) == '0') {
   $prevousWeekday = date('mdy', strtotime('- 3 day'));
} else {
   $prevousWeekday = date('mdy', strtotime('- 1 day'));
}

I was trying to do that before, but I'm having trouble with the syntax for
   if (date('w'), $weekday) == '0')

Should it be:
  if (date('w'), strtotime($weekday)) == '0')
?  I can't get it to work for some reason.
Thanks.
0
 

Author Comment

by:Randall-B
ID: 18787029
I came up with this to convert any date like "030507" to the previous weekday:

<?php

$input = "030507";

echo "$input ";
echo getPreviousWeekday($input);


function getPreviousWeekday($input) {
   $inputMonth = substr($input, 0, 2);
   $inputDay = substr($input, 2, 2);
   $inputYear = substr($input, 4, 2);
   $timestamp = strtotime("$inputYear-$inputMonth-$inputDay");
       if (date("w", $timestamp) == 1) { // input is Monday
          $previousWeekday = date('mdy', strtotime("-3 day", $timestamp));
        } elseif (date("w", $timestamp) == 0) { // input is Sunday
              $previousWeekday = date('mdy', strtotime("-2 day", $timestamp));      
          } else { // input is not Sunday or Monday
              $previousWeekday = date('mdy', strtotime("-1 day", $timestamp));
        }
    return $previousWeekday;
 }

?>


and the entire working script, which prints all weekdays (and their previousweekday) in a given month, is:


<html>
<body>

<table>

<?php

$inputDate = "March, 2007";

list($inputMonth, $inputYear) = explode(', ', $inputDate);

$daysInMonth = date('t', strtotime("$inputMonth $inputYear"));

for ($i=1; $i<=$daysInMonth; $i++)  {
      if (6 > date('N', strtotime("$i $inputMonth $inputYear"))) {
         $weekday = date('mdy', strtotime("$i $inputMonth $inputYear"));
         $previousweekday = getPreviousWeekday($weekday);
       
      echo "<tr><td>$weekday $previousweekday</td></tr>";
      }
 }

function getPreviousWeekday($input) {
   $inputMonth = substr($input, 0, 2);
   $inputDay = substr($input, 2, 2);
   $inputYear = substr($input, 4, 2);
   $timestamp = strtotime("$inputYear-$inputMonth-$inputDay");
       if (date("w", $timestamp) == 1) { // input is Monday
          $previousWeekday = date('mdy', strtotime("-3 day", $timestamp));
        } elseif (date("w", $timestamp) == 0) { // input is Sunday
              $previousWeekday = date('mdy', strtotime("-2 day", $timestamp));      
          } else { // input is not Sunday or Monday
              $previousWeekday = date('mdy', strtotime("-1 day", $timestamp));
        }
    return $previousWeekday;
 }
?>
</table>
</body>
</html>


That works, although I'm sure it could be improved.
0
 

Author Comment

by:Randall-B
ID: 18787040
And to output the list of weekdays and their previous days in reverse order (from the last weekday of the month down to the 1st weekday of the month), it works with this for . . . loop:

for ($i=$daysInMonth; $i>=1; $i--)

Thanks.
0
 

Author Comment

by:Randall-B
ID: 18787228
I'm accepting your first response as the answer, since it did work as requested in the Question (although the function in my comment above seems to work better in the context of the particular script that I'm using). Thanks!
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