Check if a file exists, with case-insensitive file name.

file-exists-ci.php

<?php

function file_exists_ci($file) {
  if (file_exists($file))
    return $file;

  $lowerfile = strtolower($file);

  foreach (glob(dirname($file) . '/*')  as $file)
    if (strtolower($file) == $lowerfile)
      return $file;

  return FALSE;
}