如何从PHP文件在HTML内部调用警报功能

Question

I am trying to add reCaptcha v2 to an HTML form. When the submit button is clicked, a PHP file is invoked which calls the reCaptcha API.

If the reCaptcha is unsuccessful, I want to call the alert function inside the HTML page from the PHP file.

I have researched a lot but I couldn't find anything for my use case. This post shows how to show alert inside PHP not inside an HTML file.

Right now when I click submit without doing reCaptcha, I've encountered a blank PHP page, but I expect to remain in the HTML form without deleting the form content and show an alert message asking the user to complete reCaptcha.

Thanks in advance!

Answer 1

That's not how this works. There's a separation of server and client side code. PHP runs on the server, then sends its results back to the browser on the client -- that is, it sends back the HTML / Javascript / CSS / etc. that the browser will show. You cannot submit a form to a PHP file and then expect PHP to call a JS function on the client side.

You should be doing this kind of validation on the client size in the first place. That means you shouldn't be waiting until the data has gotten to the PHP script before validating; you should validate that the reCaptcha is filled out with JavaScript, and if not, don't submit the form at all.