PHP gets remote pictures to local

  /*
 * Get remote image to local
 */
 function GrabImage($url){
 if($url != ""){ //If the image address is empty
 $ext = strrchr($url,'.'); //Determine the format of the image
 if($ext != '.jpg' && $ext != '.gif' && $ext != '$png'){
 return false;exit;
 }
 $filename_r = time().rand(10,9000).$ext; //Name the picture
 $filename = 'getimg/'.$filename_r;
 ob_start(); //Open the buffer Area
 readfile($url);
 $imginfo = ob_get_contents(); //Get the contents of the buffer
 ob_end_clean(); //Clear and close the buffer
 $fp = fopen($filename,'a');
 fwrite($fp,$imginfo);
 fclose($fp);
 }else{
 return false;
 }
 }
 $start_time = microtime(true);
 GrabImage("http://img4.shougongke.com /Public/advance/53846840dafb4.jpg");
 $end_time = microtime(true);
 $time = round($end_time-$start_time,3);
 echo 'Total program time'.$time.'seconds';
 ?>

PHP