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PHP: Need Help with a FOR Loop with Dynamic Incrementing

Posted on 2014-08-16
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Last Modified: 2014-09-04
Hello, I can't seem to get this and I'm exhausted from trying, my brain is fried hah.

I want:
For loop where I can specify each of the values (min, max, increment). I will let user specify these values thru CMS, it's for a wholesale page where there is restrictions.

So for example:
Minimum order: 10
Then increment from 50 from there.
So if user sets, 10 minimum, 500 maximum, and incrementing by 50

I thought I could do:

for ( $i = 10;  $i <= 500;  $i + 50)
Which obviously doesn't work. Completely fails and puts the page into an endless loop.

(Btw, I'm just using those value above for a clear example. But they will be values ($minqty (10), $maxqty (500), $qtyinc(50) )


So then I tried:

for($i=10;$i<=500;$i+$qtyinc) {
   if ($i!=10) { $i = $i + $qtyinc; }
  echo $i."<br>";
}

And I get:
10, 61, 112, 163, 214, 265, 316, 367, 418, 469, 520

Close, but no cigar.

The desired result is:
10, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500

How can i do it??

Thanks a lot for your help ! :)
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Question by:tonyhhisc
4 Comments
 
LVL 81

Accepted Solution

by:
arnold earned 2000 total points
ID: 40265187
Your increment portion is missing the equal sign
$i+=50.
Without the equal $i is incremented by the default increment of 1 seemingly when $i Is updated.

In a for loop, you if condition as well as the for loop will increment.
First run is 10.
On second run hitting the for loop, the new value will be 60
If check, will increment $i by qtyinc.
Next $i will be 60+qtyinc+50
Hitting if, another qtyinc is added.



To do what you want, you have to use a while loop
$i=10;
While ( $i<=500) {




Here you can test and either increment by 50 or by another value.
}
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LVL 111

Expert Comment

by:Ray Paseur
ID: 40265247
10 minimum, 500 maximum, and incrementing by 50
Does this mean that the client can order 10 items, but if he wants 11 he is forced to order 60 instead?  And if he wants to order 501 this is disallowed?  I'm asking because I think there may be more to the design pattern than just getting the syntax right on a for() loop.  If there is more you can tell us, maybe we can help more.
0
 
LVL 84

Expert Comment

by:Dave Baldwin
ID: 40265266
This will generate the list but you will have to add code to select the output you want.
<?php 
$quantlist = array(10, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500);
foreach($quantlist as $value) {
	echo "Quantity ".$value."<br>";
	}
?>
 

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Author Closing Comment

by:tonyhhisc
ID: 40304725
Thank you Arnold, and thanks for your detailed guidance. Much appreciated!

Thanks for your comments Ray.

And thank you Dave, but since the numbers will be entered by the site owner through a CMS it has to work dynamically.
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