PHP Booleans:

trscookie · 07-29-2010, 06:35 PM

Hello All,

I have this function that is supposed to print draw the first image from a function then hide the rest of the images using 'display: none' however for some reason the boolean test does not seem to work on one of my servers however it works on another, is there some php.ini setting I am missing or can you see any issues with the following code:

Code:

        $FIRST = TRUE;          
    
        for($i = 0; $i<count($imageID); $i++)
          {                             
          $id = $imageID[$i];           
                                            
          echo "<a";   
// The following IF statement fails, even when it is $FIRST==FALSE                 
            if(!$FIRST)                         
              {
    // THIS CODE IS ALWAYS EXECUTED.                                         
              echo  " style = 'display: none;'";        
              }                                         
          echo "                        
            rel='example_group'
            title='Custom title'
            href='getimage.php?id=$id'>
            
            <img
              src = 'getimage.php?id=$id'
              style   = 'border:      none'
              width   = '60px'
              height  = '60px'
              />";
                                            
          $FIRST = FALSE;               
          }

Please can you tell me why that statement is always executed on one server and works correctly on another?

Many thanks in advance.
trscookie.

jlinkels · 07-29-2010, 07:01 PM

PHP implementation of booleans is flawed in my opinion, but that is because of the non-typedness of the language. Therefore the '===' operator has been created. Which doesn't work for me half of the time either.

A variable is not false when it has a non-zero value. So if $FIRST = FALSE; , $FIRST is a non-zero value and therefor true!

I would not rely on this mechanism. A few alternatives:

PHP Code:



$FIRST=TRUE; 
if ($FIRST === TRUE)

Not recommended because I have seen in failing.

PHP Code:



$FIRST=1 
if ($FIRST)

Will work, but relies on the implementation of boolean evaluation.

PHP Code:



$FIRST=1 
if ($FIRST == 1)

Best. Unambiguous. Works always.

jlinkels