Calling javascript function in my PHP code

Question

I searched up some questions on stackoverflow and used the suggested solutions, however, I can't seem to get my php code working the way I'd like.

When I visit projects.php?message=success or projects.php?message=removed, the JavaScript function does not execute. In my debugging, I've confirmed the JavaScript is working correctly by attaching it to a button with the onclick property.

My php code:

<?php 
function GET($key) {
    return isset($_GET[$key]) ? $_GET[$key] : null;
}

$alert= GET('message');
if ($alert == success) {
    echo '<script type="text/javascript"> window.onload=success(); </script>';
} elseif ($alert == removed) {
    echo '<script type="text/javascript"> window.onload=removed(); </script>';
}

?>

My JavaScript code:

    <script>
    function success() {
        $.notify({
            // options
            icon: "pe-7s-cloud-upload",
            message: 'New project entry was successfully added.' 
        },{
            // settings
            type: 'success'
        });
    }
    function removed() {
        $.notify({
            // options
            icon: "pe-7s-trash",
            message: 'Project entry was successfully deleted.' 
        },{
            // settings
            type: 'danger'
        });
    }
</script>

Answer 1

I've tested is the inexistent constant you're using called success. As @Chris G said

Change the if for :

if ($alert == "success")

Answer 2

You need quotes around the texts and properly set window.onload:

<?php 
function GET($key) {
    return isset($_GET[$key]) ? $_GET[$key] : null;
}

$alert = GET('message');
echo "<script>window.onload = function () { ";
if ($alert == "success") echo "success();";
else if ($alert == "removed") echo "remove();";
echo " };</script>";
?>

If those two are all you need, you can also do this:

$alert = GET('message');
if ($alert == "success" || $alert == "remove") {
    echo "<script>window.onload = $alert;</script>";
}

Edit:
To clarify an issue from the comments: to set window.onload to a function, one cannot use

window.onload = myFunc();  // WRONG!

(This will call the function, then set window.onload to the result)

The correct way is:

window.onload = myFunc;
// OR
window.onload = function () {
  myFunc();
};