How to Call PHP Function on Button Click?

In PHP web development, PHP code is executed on the server-side before the page is sent to the user’s browser. This means you cannot call a PHP function directly when a button is clicked in the browser—unlike JavaScript. However, you can trigger a PHP function as a result of a user action (like clicking a button) by submitting a form (page reload/post) or making an AJAX request.

Below are the most common and practical methods to run PHP functions on button click:

1. Using an HTML Form (Page Reload Method)

Here, clicking the button submits the form to the same or another PHP script, which can then call the PHP function.

Example:

<?php
function showAlert() {
    echo "<script>alert('Button clicked! PHP function executed.');</script>";
}

if(isset($_POST['myButton'])) {
    showAlert();
}
?>
<form method="post">
    <button type="submit" name="myButton">Click Me</button>
</form>

How it works?

The button submits the form.
PHP checks if the button was clicked using isset($_POST['myButton']).
The PHP function runs on server-side and outputs a JavaScript alert.

2. Using AJAX (No Page Reload, More Dynamic)

With AJAX (using JavaScript/jQuery), you can send a request to PHP when a button is clicked, and PHP can respond. This does not reload the page.

HTML + JavaScript:

<button id="callPhp">Call PHP Function</button>
<div id="result"></div>

<script>
document.getElementById("callPhp").onclick = function(){
    fetch("ajax-handler.php", { method: "POST" })
      .then(response => response.text())
      .then(data => document.getElementById("result").innerHTML = data);
}
</script>

ajax-handler.php

<?php
function getMessage() {
    return "This message is from a PHP function!";
}

echo getMessage();
?>

3. Using URL Query Strings (GET Method)

For simple get requests, clicking a link/button can append a parameter to the URL and PHP can check and run a function:

<?php
function greet() {
    echo "Hello from PHP function!";
}

if(isset($_GET['greet'])) {
    greet();
}
?>
<a href="?greet=1"><button>Greet</button></a>

Summary Table

Method	Page Reload	More Dynamic	Usage
Form POST/GET	Yes	No	Simple actions/forms
AJAX	No	Yes	No reload, modern SPA
URL Query (GET)	Yes	No	Simple url-based calls

Important Note

PHP code runs on the server. You can only “call a PHP function on button click” by re-submitting data to the server (with a form or AJAX).
For client-side interactivity (without reloads), use AJAX to call a server-side PHP script.