What for do we use CURLOPT_WRITEFUNCTION in PHP's cURL?

Question

Could you describe it in examples, please?

Answer 1

I know this is an old question, but maybe my answer will be of some help for you or someone else. The WRITEFUNCTION is useful for processing text as it comes streaming in or for aborting the download based on some condition. Here's an example that simply puts all the text into uppercase letters:

function get_html($url){
    $ch = curl_init();
    $obj = $this;//create an object variable to access class functions and variables
    $this->result = '';
    $callback = function ($ch, $str) use ($obj) {
        $obj->result .= strtoupper($str);
        return strlen($str);//return the exact length
    };
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_HEADER, 0);
    curl_setopt($ch, CURLOPT_WRITEFUNCTION, $callback);
    curl_exec($ch);
    curl_close($ch);
    return $this->result;
}

To see how I used it, check out this link: Parallel cURL Request with WRITEFUNCTION Callback.