I wrote some code to upload an image to a server. Now I wanted to add a function "imageresize" wich resizes the image to a predefinded height and width. When I run it I get a fatal error
what I've tried: I found a simple piece of code on the internet witch works and tried the same stucture in my script
<?php
function voegGebruikerToe ($naam, $Ww, $WwConfirm, $sqlInsert, $nameImage, $naamDiv) {
    if(!empty($naam) and !empty($Ww) and !empty($WwConfirm)){
        if ($Ww == $WwConfirm) {
            $passHash = password_hash($Ww, PASSWORD_DEFAULT); // Creates a password hash
            $sql1 = "INSERT INTO users (username, password) VALUES ('$naam', '$passHash')";        
            if ($sqlInsert->query($sql1) === TRUE) {            //insert invevoerde data to database
                echo "ok";              
            } else {
            }
        } else {
            echo "your passwords doesn't match";
        }
    } else{
        echo "Please enter all the fields.";
    }
    $file = $_FILES[$naamDiv]['tmp_name']; 
    $sourceProperties = getimagesize($file);
    $fileNewName = $nameImage;
    $folderPath = "/var/www/";
    $ext = pathinfo($_FILES[$naamDiv]['name'], PATHINFO_EXTENSION);
    $imageType = $sourceProperties[2];
    $imageFileType = strtolower(pathinfo($_FILES[$naamDiv]['name'],PATHINFO_EXTENSION));
            // Allow certain file formats
    if($imageFileType != "jpg" && $imageFileType != "png" && $imageFileType != "jpeg"
    && $imageFileType != "gif" ) {
        echo "Sorry, only JPG, JPEG, PNG & GIF files are allowed. <br>";
    } else {
        switch ($imageType) {
            case IMAGETYPE_PNG:
                $imageResourceId = imagecreatefrompng($file); 
                $targetLayer = imageResize($imageResourceId,$sourceProperties[0],$sourceProperties[1]);
                imagepng($targetLayer,$folderPath. $fileNewName. ".". $ext);*/
                break;
            case IMAGETYPE_JPEG:
                $imageResourceId = imagecreatefromjpeg($file); 
                $targetLayer = imageResize($imageResourceId,$sourceProperties[0],$sourceProperties[1]);
                imagejpeg($targetLayer,$folderPath. $fileNewName. ".". $ext);*/
                echo "works";
                break;
            default:
                echo "Invalid Image type.";
                exit;
                break;
        }
        //move_uploaded_file($file, $folderPath. $fileNewName. ".". $ext);
        echo "Image Resize Successfully.";
    }
    function imageResize($imageResourceId,$width,$height) {
        $targetWidth =200;
        $targetHeight =200;
        $targetLayer=imagecreatetruecolor($targetWidth,$targetHeight);
        imagecopyresampled($targetLayer,$imageResourceId,0,0,0,0,$targetWidth,$targetHeight, $width,$height);
        return $targetLayer;
    }   
}
voegGebruikerToe($admNaam, $admWw, $admWwConfirm, $conn, "administrator", "ImageUser1");
?>
the example code I found:
<?php
function x ($y) {
    function y ($z) {
        return ($z*2);
    }
    return($y+3);
}
$y = 4;
$y = x($y)*y($y);
echo $y;
?>
Fatal error: Uncaught Error: Call to undefined function imageResize() in /var/www/html/v0.2_webpagina_barchart (setupPage)/php/setUpPHP.php:75 Stack trace: #0 /var/www/html/v0.29_webpagina/php/setUpPHP.php(146): voegGebruikerToe('t', 't', 't', Object(mysqli), 'administrator', 'ImageUser1') #1 /var/www/html/v0.2_webpagina /setUp.php(4): include('/var/www/html/v...') #2 {main} thrown in /var/www/html/v0.2_webpagina/php/setUpPHP.php on line 75