Infinite while loop issue with PHP

Question

I'm using the same while loop on two pages where the only difference is a different SQL call on each page. The first works as it should, grabbing the contents from the query and displaying it in an image slider:

  <?php

            $qry = mysql_query(sprintf("SELECT * FROM manageme WHERE element IN ('%s')", $element));
            $i = 0;
            while (($t = mysql_fetch_array($qry)) != null && $i < 52) { $i++;?>
                <li>


                    <a href="">                                                           
                        <img src="<?php print $t['fileLocation']; ?>"; 
                        title="<?php print $t['element_name']; ?>"; 
                        name="<?php print $t['clickLocation']; ?>";
                        alt="wat" 
                        class="btnshow" />
                    </a>
                </li>
<?php } ?>

This works as it should stepping through the loop and grabbing the contents from the query so long as there are less than 52 entries returned, ending when each record has displayed once.

Upon implementing the same while loop with a different SQL call, the problem occurs.

      <?php

$qry = mysql_query(sprintf("SELECT u.username, us.user_id, us.service_id,
                                        s.imageID, s.title, s.clickLocation, s.fileLocation, s.element_name
                                        FROM user u, user_service us, manageme s
                                        WHERE us.user_id = %s
                                        AND s.imageID = us.service_id", $_COOKIE['user_id']));
            $i = 0;
            while (($t = mysql_fetch_array($qry)) != null && $i < 52) { $i++;?>
                <li>


                    <a href="">                                                           
                        <img src="<?php print $t['fileLocation']; ?>"; 
                        title="<?php print $t['element_name']; ?>"; 
                        name="<?php print $t['clickLocation']; ?>";
                        alt="wat" 
                        class="btnshow" />
                    </a>
                </li>
<?php } ?>

Instead of grabbing from the array and ending the while loop when the contents have displayed once, it continues to loop the contents in the image slider until 52 entries have been displayed. So for instance, if the SQL call only finds 4 records to display in the image slider, the set of 4 displays 13 times (52/4) before ending the loop.

Can anyone help me figure out how to end this loop after it has displayed each record from my database once and only once? Thanks in advance!

why not limit the results in the mysql query? that will solve the infinite loop problem and will be no need for the $i limiting loop variable — SoniCoder
– SoniCoder, Commented Nov 9, 2012 at 15:00
@Blacksonic exactly. What the OP is doing here is unnecessary. — Geoff Montee
– Geoff Montee, Commented Nov 9, 2012 at 15:00

Teena Thomas · Accepted Answer · 2012-11-09 15:01:19Z

1

Try adding LIMIT 52 to your query, and do the while loop as,

  while ($t = mysql_fetch_array($qry)) {
  //do something
  }

answered Nov 9, 2012 at 15:01

Teena Thomas

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Comments

Marc B · Accepted Answer · 2012-11-09 14:58:31Z

0

Major problems:

1) Vulnerable to SQL injection attacks. Enjoy having your server destroyed.

2) Terminology: you're not fetching "from an array". You're fetching a row of data from a result set, returning that row AS an array.

3) Your loop should terminate after 52 records OR no more records are avaialble, even though you're using some ugly syntax in the while() condition. Check that your query is actually fetching the right records, in the order/format you're expecting. There's nothing in your code that'd cause PHP to output "duplicate" rows.

answered Nov 9, 2012 at 14:58

Marc B

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1 Comment

user1809737 Over a year ago

Thank you for the heads up Marc. I'm still quite new to PHP so insights from people in the know are highly valued. After getting rid of the while loop and adding LIMIT 52 to the end of the query like others had suggested I yielded the same unfortunate result of a loop that ends only after 52. The problem was my query, I was grabbing every user from the user table by including SELECT u.username with everything else. Getting rid of it grabs only the records I needed. I very much appreciate the help guys!

Emmanuel N · Accepted Answer · 2012-11-09 14:58:41Z

0

use mysql_num_rows($qry) to terminate the loop in addition to < 52

Something like:

 (($t = mysql_fetch_array($qry)) != null && ($i < mysql_num_rows($qry) || $i < 52))

answered Nov 9, 2012 at 14:58

Emmanuel N

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Comments

Grambot · Accepted Answer · 2012-11-09 14:59:50Z

0

From the manual it seems that your call to mysql_fetch_array($qry) will never return null. At the end of the result set you will get a false return. If you change your conditional to check for this you should be able to terminate the loop

answered Nov 9, 2012 at 14:59

Grambot

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1 Comment

Oliver A. Over a year ago

But he is not doing a strict comparison. 'null != false' is false

Geoff Montee · Accepted Answer · 2012-11-09 15:00:05Z

0

Get rid of the $i < 52 check. Instead add LIMIT 52 to the end of your SQL query. Then change the while loop to:

while ($t = mysql_fetch_array($qry)) {
....
}

answered Nov 9, 2012 at 15:00

Geoff Montee

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