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PHP Loops

by Crayon Violent on Jun 19, 2008 2:46:30 PM

The Code

Okay the first thing I am going to do is give you the complete script for the solution to this problem. That way, you have the goods right up front and can refer to it as a whole.

<?php

// variable to hold form
$form = <<<SOMEFORM
<form action = '{$_SERVER['PHP_SELF']}' method = 'post'>
   Range Start: <input type = 'text' name = 'start' size = '3'><br />
   Range Finish: <input type = 'text' name = 'finish' size = '3'><br />
   Divided By: <input type = 'text' name = 'num' size = '3'><br />
   <input type = 'submit' value = 'Find Numbers'>
</form>
SOMEFORM;

// if we have posted info...
if ($_POST) {
   // assign post vars to reg vars for easier handling
   $start = (int) $_POST['start'];
   $finish = (int) $_POST['finish'];
   $num = (int) $_POST['num'];

echo "The following numbers from $start to $finish are divisible by $num : <br />";
   // loop from $start to $finish, 1 number at a time
   for ($x = $start; $x <= $finish; $x++) {
      // if the modulus of the current number and the divided by number
      // is zero, then it is evenly divisible by that number
      if (($x % $num) == 0) {
         // echo the number
         echo "$x ";
      } // end if
   } // end for
} // end if

// echo out the form
echo $form;

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Comments

Again, very nice CV. Only thing i would mention is that it's not strictly true that a for loop requires all 3 parameters. This is a perfectly valid for loop:

<?php for($x=0;;){ } ?>
As is this:

<?php for(;$x<5;){ } ?>
Of course, they serve no real useful purprose (use a while loop, it's easier to follow) but i had to find something wrong with it :P

1. Ben Smithers on Jun 20, 2008 5:07:40 AM

Ah you are right, but in order for the loops to function properly, they still need to have all the components somewhere. Your first example, while syntactically correct, would in and of itself be an infinite loop. Using your first example, you would have to put the condition and iteration inside the instruction. Example:

<?php for($x=0;;) { if ($x > 10) break; $x++; }

I'm glad you pointed that out though : )

2. Crayon Violent on Jun 20, 2008 10:19:46 AM

A concise explanation of loops. Very good.

3. kahratka on Jun 20, 2008 10:32:40 AM