试试这个:

function grab_image($url,$saveto){
    $ch = curl_init ($url);
    curl_setopt($ch, CURLOPT_HEADER, 0);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_BINARYTRANSFER,1);
    $raw=curl_exec($ch);
    curl_close ($ch);
    if(file_exists($saveto)){
        unlink($saveto);
    }
    $fp = fopen($saveto,'x');
    fwrite($fp, $raw);
    fclose($fp);
}

并确保在php.ini中启用allow_url_fopen

and ensure that in php.ini allow_url_fopen is enable