Enable or disable interlace in PHP

<?php/* ww  w. j a  v a 2s.  co m*/
// Create an image instance
$im = imagecreatefromgif('php.gif');

// Enable interlancing
imageinterlace($im, true);

// Save the interlaced image
imagegif($im, './php_interlaced.gif');
imagedestroy($im);
?>