[php] How do I show multiple recaptchas on a single page?

This answer is an extension to @raphadko's answer.

If you need to extract manually the captcha code (like in ajax requests) you have to call:

grecaptcha.getResponse(widget_id)

But how can you retrieve the widget id parameter?

I use this definition of CaptchaCallback to store the widget id of each g-recaptcha box (as an HTML data attribute):

var CaptchaCallback = function() {
    jQuery('.g-recaptcha').each(function(index, el) {
        var widgetId = grecaptcha.render(el, {'sitekey' : 'your code'});
        jQuery(this).attr('data-widget-id', widgetId);
    });
};

Then I can call:

grecaptcha.getResponse(jQuery('#your_recaptcha_box_id').attr('data-widget-id'));

to extract the code.