PHP display images if else statment

There are several issues here.

1. Be careful about your comparison operator - you currently are reassigning the $files array in this line:

   if ($files = array("gif", "jpeg", "jpg", "png");) {
   

2. You are comparing your $files array to another array in a meaningless way. You could potentially build out a separate $images array, as it looks like you're trying to do, but this would be better accomplished within the foreach loop, as in:

   foreach($files as $file) {
     $filepath = pathinfo($file);
     if (in_array($filepath['extension'], ('gif', 'jpeg', 'jpg', 'png')) {
       $image = $file;
     } else {
       $image = 'http://hg.exbabylon.net/find_fitter/placeholder.jpg';
     }
   
     echo '<div class="one_half"><img src="' . $images . '" class="images" /></br><h2>' .basename($file). '</h2><a class="download" href="fitter/download.php?file='.base64_encode($file).'"></a></div>';
   }
   

3. Ideally, you should be looking at mime type rather than file extension. In PHP 5.3, this is done as follows:

   $finfo = finfo_open(FILEINFO_MIME_TYPE); // return mime type ala mimetype extension
   $mimetype = finfo_file($finfo, $file);
   finfo_close($finfo);
   

You can then do a comparison based on the mime type as in (2).

<?php
    $allowed_extensions = array("gif", "jpeg", "jpg", "png");

    // use values as keys for lasier lookups
    $allowed_extensions = array_combine($allowed_extensions, $allowed_extensions);

    // Find all files in that folder
    $files = glob('files/*');

    // Do a natural case insensitive sort, usually 1.jpg and 10.jpg would come next to each other with a regular sort
    natcasesort($files);

    // Display images
    foreach($files as $file) {

       // split file name at "." and use last part as file extension
       $file_parts = explode('.', $file);
       $file_extension = array_pop($file_parts)

       // check if file extensions is allowed
       if($allowed_extensions[$file_extension]) {
           $images = $file;
       } else {
           $images = "http://hg.exbabylon.net/find_fitter/placeholder.jpg";
       }

       echo '<div class="one_half"><img src="' . $images . '" class="images" /></br><h2>' .basename($file). '</h2><a class="download" href="fitter/download.php?file='.base64_encode($file).'"></a></div>';
    }

?>

Assuming that your $files holds just a file name + extension i.e. myimage.png

foreach($files as $file) {
   $split = explode(".", $file);
   $extension = array_pop($split);

   if (in_array($extension, array('gif', 'jpeg', 'jpg', 'png'))) {
      $images = $file;
   } else {
      $images = "http://hg.exbabylon.net/find_fitter/placeholder.jpg";
   }

   //display your image
   echo '<div ...';
}

Change it into something like this

<?php

        // Find all files in that folder
        $files = glob('files/*');

        // Do a natural case insensitive sort, usually 1.jpg and 10.jpg would come next to each other with a regular sort
        natcasesort($files);

        $extensions = array("gif", "jpeg", "jpg", "png");

        // Display images
        foreach($files as $file) {
           $pi - pathinfo($file);
           if(!in_array($pi['extension'], $extensions)) {
              $file = "http://hg.exbabylon.net/find_fitter/placeholder.jpg";
           }

           echo '<div class="one_half"><img src="' . $file . '" class="images" /></br><h2>' .basename($file). '</h2><a class="download" href="fitter/download.php?file='.base64_encode($file).'"></a></div>';
        }

    ?>

You can use regular expressions and the preg_match function:

if (preg_match("/.*\.gif|jpg|jpeg|png$/i", $files)) {
  $images = $file
} else {
  $images = "http://hg.exbabylon.net/find_fitter/placeholder.jpg";
}

Also, see preg_match documentation.

Note: it would be better to check the mime-type (if possible), because filename can be easily changed.