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While loop not working as expected with variable

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By User



The following code works fine when i remove the && $f<4 , but with it in, it doesn't work.





PHP:







$titles=array();

$f=0;

while ($row=mysql_fetch_assoc($query) && $f<4){  //this line doesn't work

        $titles[]=$row['questiontitle'];

            echo "<div class='questionPreview'>$titles[$f]</div>";

            $f++;

        }




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Comments

  1. Tips For AllJanuary 30, 2012 at 2:08 AM

    If I interpret you correctly I think you are having a precedence problem. Try this:

    while (($row=mysql_fetch_assoc($query)) && ($f<4)){

    ReplyDelete
  2. Tips For AllJanuary 30, 2012 at 2:08 AM

    =has lower precedence than&&. This means that the && operator is evaluated first.

    This means that your code, in effect, looks like this:

    while ($row = (mysql_fetch_assoc($query) && $f<4)){ //this line doesn't work


    So, in other words, do the MySQL query and the comparison, and if they are both true, set $row to true; otherwise, set it to false.

    You need to use brackets to ensure that the right operations are done:

    while (($row=mysql_fetch_assoc($query)) && ($f<4)){

    ReplyDelete
  3. Tips For AllJanuary 30, 2012 at 2:08 AM

    That is probably because $row is true rather then the array:

    $ php -r 'var_dump($row = pow(2,2) && true,$row);'
    bool(true)
    bool(true)
    $ php -r 'var_dump($row = pow(2,2) && false,$row);'
    bool(false)
    bool(false)


    (pow being a random function here)

    That is because && has a higher precedence then =. As always, solve with ():

    while ( ($row = mysql_fetch_assoc($query) ) && $f<4){

    ReplyDelete

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