How to call a php function from ajax?

You cannot call a PHP function directly from an AJAX request, but you can do this instead:

<? php 
    function test($data){
        return $data+1;
    }

    if (isset($_POST['callFunc1'])) {
        echo test($_POST['callFunc1']);
    }
?>
<script>
    $.ajax({
        url: 'myFunctions.php',
        type: 'post',
        data: { "callFunc1": "1"},
        success: function(response) { console.log(response); }
    });
</script>

As a structure for this kind of purposes, I suggest this:

PHP

<?php
    if(isset($_POST['action'])){
        if ($_POST['action'] == "function1") { func1(); }
        if ($_POST['action'] == "function2") { func2(); }
        if ($_POST['action'] == "function3") { func3(); }
        if ($_POST['action'] == "function4") { func4(); }
    }

    function func1(){
        //Do something here
        echo 'test';
    }
?>

jQuery

var data = { action: 'function1' };

$.post(ajaxUrl, data, function(response) {
    if(response != "") {
        $('#SomeElement').html(response);
    }else{
        alert('Error, Please try again.');
    }
});

As mentioned, you can't call a PHP function directly from an AJAX call.

For AJAX request

1. Include jQuery Library in your web page. For e.g.

   <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
   

2. Call a function on button click

   <button type="button" onclick="create()">Click Me</button>
   

3. While click on button, call create function in JavaScript.

   <script>
       function create () {
           $.ajax({
               url:"test.php",    //the page containing php script
               type: "post",    //request type,
               dataType: 'json',
               data: {registration: "success", name: "xyz", email: "[email protected]"},
               success:function(result){
                   console.log(result.abc);
               }
           });
       }
   </script>
   

On the server side test.php file, the action POST parameter should be read and the corresponding value and do the action in PHP and return in JSON format e.g.

$registration = $_POST['registration'];
$name= $_POST['name'];
$email= $_POST['email'];

if ($registration == "success"){
    // some action goes here under php
    echo json_encode(array("abc"=>'successfuly registered'));
}