Calling a PHP function from an HTML form in the same file

Question

I'm trying to execute a PHP function in the same page after the user enters a text and presses a submit button.

The first I think of is using forms. When the user submits a form, a PHP function will be executed in the same page. The user will not be directed to another page. The processing will be done and displayed in the same page (without reloading).

Here is what I reach to:

In the test.php file:

<form action="test.php" method="post">
    <input type="text" name="user" placeholder="enter a text" />
    <input type="submit" value="submit" onclick="test()" />
</form>

The PHP code [ test() function ] is in the same file also:

<?php
    function test() {
        echo $_POST["user"]; // Just an example of processing
    }
?>

However, I still getting a problem! Does anyone have an idea?

Answer 1

You have a big misunderstanding of how the web works.

Basically, things happen this way:

• User (well, the browser) requests test.php from your server
• On the server, test.php runs, everything inside is executed, and a resulting HTML page (which includes your form) will be sent back to browser
• The browser displays the form, the user can interact with it.
• The user submits the form (to the URL defined in action, which is the same file in this case), so everything starts from the beginning (except the data in the form will also be sent). New request to the server, PHP runs, etc. That means the page will be refreshed.

You were trying to invoke test() from your onclick attribute. This technique is used to run a client-side script, which is in most cases Javascript (code will run on the user's browser). That has nothing to do with PHP, which is server-side, resides on your server and will only run if a request comes in. Please read Client-side Versus Server-side Coding for example.

If you want to do something without causing a page refresh, you have to use Javascript to send a request in the background to the server, let PHP do what it needs to do, and receive an answer from it. This technique is basically called AJAX, and you can find lots of great resources on it using Google (like Mozilla's amazing tutorial).

Answer 2

This cannot be done in the fashion you are talking about. PHP is server-side while the form exists on the client-side. You will need to look into using JavaScript and/or Ajax if you don't want to refresh the page.

test.php

<form action="javascript:void(0);" method="post">
    <input type="text" name="user" placeholder="enter a text" />
    <input type="submit" value="submit" />
</form>

<script type="text/javascript">
    $("form").submit(function(){
        var str = $(this).serialize();
        $.ajax('getResult.php', str, function(result){
            alert(result); // The result variable will contain any text echoed by getResult.php
        }
        return(false);
    });
</script>

It will call getResult.php and pass the serialized form to it so the PHP can read those values. Anything getResult.php echos will be returned to the JavaScript function in the result variable back on test.php and (in this case) shown in an alert box.

getResult.php

<?php
    echo "The name you typed is: " . $_REQUEST['user'];
?>

NOTE

This example uses jQuery, a third-party JavaScript wrapper. I suggest you first develop a better understanding of how these web technologies work together before complicating things for yourself further.