PHP extracts and downloads the image address in the css file

/**
* Get the image address in CSS and save it locally
*/
class getInCssImage
{
/**
 * Save the picture
 * @param $cssUrl css url address
 * @param $dir The directory where the picture is saved
 * @return void
*/
static public function saveImage($cssUrl, $dir)
{
$content = file_get_contents($cssUrl) ;
$patterns = '/images(.*).(jpg|gif|png)/'; //regex needs to be transformed according to different addresses
preg_match_all($patterns, $content, $matches);
$imagesUrls = $matches [0];
if (!is_dir($dir))
mkdir(dirname(__FILE__). '/'. $dir, 0777);
foreach($imagesUrls as $image)
{
ob_start();
$ imageUrl = "http://www.plcxue.com/".$image; //The address to be captured
readfile($imageUrl);
$img = ob_get_contents();
ob_end_clean();
$size = strlen ($img);
$localImage = $dir. strchr($image, '/'); //Save the local image address
$fp = fopen($localImage, 'a');
fwrite($fp, $img);
fclose($fp);
}
}
}
$content = getInCssImage::saveImage('/css/css.css', 'image');