How to validate reCAPTCHA

Question

I want to write a JavaScript and php validation for reCAPTCHA In my php I have the function below but I doesn't work. It doesn't, return an errror message if I enter the wrong reCAPTCHA code:

function invalid($inputname,$error_message)
{
    $this->js.='if (!invalid(formname.'.$inputname.',"'.$error_message.'")) return false;';
    if ( isset($_POST[$inputname]) && strlen($_POST[$inputname]) - strlen(str_replace(' ','',$_POST[$inputname])) > $limit && $_POST[$inputname] != "")
    {
        $this -> error_message .= $error_message.'<br>';
    }
}

I don't want to just echo the message I want to echo the message on top of the form like I did with my other validate using:

Can someone show me how to do it correctly in php and javascript?

Thanks

Answer 1

Please read the reCAPTCHA documentation . It clearly outlines the correct use of the recaptcha_check_answer() function (part of the reCAPTCHA PHP library) to validate solutions.

Answer 2

This

strlen($_POST[$inputname]) - strlen(str_replace(' ','',$_POST[$inputname])) > $limit

will be false, assuming $limit is something like 6. Should be just

strlen(str_replace(' ','',$_POST[$inputname])) > $limit

Let's say the captcha is "bananas". strlen("bananas") - strlen("bananas") == 0 .

Added The JavaScript doesn't return false at any point, so it will return undefined if the captcha is correct, which may affect your code elsewhere (particularly if you are using === ).