The PHP function is returning an undefined value in JavaScript

Question

The PHP function is returning an undefined value in JavaScript

I feel like there must be a simple solution to this problem that I just can't seem to find. Everything related to PHP search functions and queries is functioning properly, except for the fact that the data isn't displaying correctly in the text area translated. Below you will see the code snippet.

document.getElementById("translated").innerHTML = xmlhttp.open("GET","ajax-result.php?result="+num,true);

Following the innerHTML section, any additional content that I insert (whether it's text or HTML) appears in the right place except that currently, the above code is returning as undefined.

javascript ajax

Answer 1

Answer №1

xmlhttp.open doesn't actually return anything, which is why you're seeing "undefined". To understand more about this issue, I recommend reading http://www.w3schools.com/ajax/ajax_xmlhttprequest_send.asp, with a special focus on the xmlhttp.onreadystatechange part.

A much more convenient approach to handling this situation is by utilizing the powerful jquery ajax method. You can find more information about it here: http://api.jquery.com/jQuery.ajax/

Answer 2

xmlhttp.open doesn't actually return anything, which is why you're seeing "undefined". To understand more about this issue, I recommend reading http://www.w3schools.com/ajax/ajax_xmlhttprequest_send.asp, with a special focus on the xmlhttp.onreadystatechange part.

A much more convenient approach to handling this situation is by utilizing the powerful jquery ajax method. You can find more information about it here: http://api.jquery.com/jQuery.ajax/

Answer 3

Answer №2

One important thing to note about ajax is the necessity of a callback function to handle server responses.

Here is an example:

if (window.XMLHttpRequest) {
        xmlhttp=new XMLHttpRequest();
}
// setting up the callback function
xmlhttp.onreadystatechange=function(){
    if (xmlhttp.readyState==4 && xmlhttp.status==200){
        if(xmlhttp.responseText == 1){
            document.getElementById("translated").innerHTML = xmlhttp.responseText;
        }
    }
}
xmlhttp.open("GET",'your request to server',true);

Answer 4

One important thing to note about ajax is the necessity of a callback function to handle server responses.

Here is an example:

if (window.XMLHttpRequest) {
        xmlhttp=new XMLHttpRequest();
}
// setting up the callback function
xmlhttp.onreadystatechange=function(){
    if (xmlhttp.readyState==4 && xmlhttp.status==200){
        if(xmlhttp.responseText == 1){
            document.getElementById("translated").innerHTML = xmlhttp.responseText;
        }
    }
}
xmlhttp.open("GET",'your request to server',true);

Answer 5

Answer №3

For a smoother experience, I recommend getting acquainted with jQuery.

Below is a fully functional example that illustrates what you are trying to achieve.

The inclusion of the input and button was just to demonstrate how a value is specified and the function is triggered.

<!DOCTYPE html>
<html>
    <head>
        <script type="text/javascript" src="http://code.jquery.com/jquery-1.10.1.min.js"></script>
    </head>
    <body>
        <script type="text/javascript">
            function runAjax(number) {
                $.ajax({
                    'url': 'ajax-result.php',
                    'type': 'GET', // Can also be 'POST'
                    'data': {
                        'result': number
                    },
                    'success': function(result) {
                        $('#translated').html(result);
                        alert('Success!');
                    },
                    'error': function(xhr, status, exception) {
                        alert('Error occurred with status code: ' + status);
                    }
                });
            }

            $(document).ready(function() {
                $('button').click(function() {
                    var $input = $('input');
                    var number = $input.val();
                    runAjax(number);
                });
            });
        </script>

        <input type="text" name="number" value="123" />
        <button type="button">Click Me!</button>
    </body>
</html>

Answer 6

For a smoother experience, I recommend getting acquainted with jQuery.

Below is a fully functional example that illustrates what you are trying to achieve.

The inclusion of the input and button was just to demonstrate how a value is specified and the function is triggered.

<!DOCTYPE html>
<html>
    <head>
        <script type="text/javascript" src="http://code.jquery.com/jquery-1.10.1.min.js"></script>
    </head>
    <body>
        <script type="text/javascript">
            function runAjax(number) {
                $.ajax({
                    'url': 'ajax-result.php',
                    'type': 'GET', // Can also be 'POST'
                    'data': {
                        'result': number
                    },
                    'success': function(result) {
                        $('#translated').html(result);
                        alert('Success!');
                    },
                    'error': function(xhr, status, exception) {
                        alert('Error occurred with status code: ' + status);
                    }
                });
            }

            $(document).ready(function() {
                $('button').click(function() {
                    var $input = $('input');
                    var number = $input.val();
                    runAjax(number);
                });
            });
        </script>

        <input type="text" name="number" value="123" />
        <button type="button">Click Me!</button>
    </body>
</html>

The PHP function is returning an undefined value in JavaScript

Answer №1

Answer №2

Answer №3

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