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Load random images within a session

2009-07-23

This function returns the path to a random image. In addition it won’t allow the same
image to be loaded repeatedly in a single re-load. ( view demo )

<?php

ob_start();
function session_random_img($min, $max) {
  session_name('rand_img');
  session_start();

  // setting
	$path = 'images';
	$file_prefix = 'background_';
	$extension = '.jpg';

  // first run
  if (empty($_SESSION['rand_img'])):
      $_SESSION['rand_img'] = mt_rand($min, $max);
      $output = $_SESSION['rand_img'];
  else:
  
    // second run
    $i = $_SESSION['rand_img'];         // retrieve the already existing value
    
    $k = mt_rand($min, $max);
      if ($k == $i) {
        while ($i == $k) {
          $k = mt_rand($min, $max);
          if ($k != $i) {               // as soon as $k is != than $i break while loop
            break;
          }
        }
      }
    $_SESSION['rand_img'] = $k;
    $output = $_SESSION['rand_img'];
      
  endif;
  $return_output = $path . '/' . $file_prefix . $output . $extension;
  return $return_output;
  ob_end_flush();
}
?>

<html>
<img src="<?php echo session_random_img(1, 5);?>" />
</html>