function imagefromURL($image,$rename)
{
$ch = curl_init($image);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_BINARYTRANSFER,1);
$rawdata=curl_exec ($ch);
curl_close ($ch);
$fp = fopen("$rename",'w');
fwrite($fp, $rawdata); 
fclose($fp);
}

<?php
$url = "http://koonk.com/images/logo.png";
$rename = "koonk.png";
imagefromURL($url,$rename);
?>