Answered Formit2file + Formit2db + Migx

<?php

/*
Formit hook to upload a file with certain restrictions:

path - path to upload files to from root
extensions - comma seperated list with extensions to allow uploading
maxsize - maximum filesize in bytes allowed
minsize - minimum filesize in bytes allowed

*/

//function to clean a string
function clean($string) {
    $string = str_replace(' ', '-', $string); // Replaces all spaces with hyphens.
    return preg_replace('/[^A-Za-z0-9\-]/', '', $string); // Removes special chars.
}

$path; // Path from root that user specifies
$extensions; // allow file extensions
$minsize; //minimum filesize in bytes
$maxsize; // maximum filesize in bytes

//define subdirectory by chose theme
$thema = strtolower($hook->getValue('thema'));

//naam ophalen en netjes maken
$naam = strtolower($hook->getValue('naam'));
$naam = str_replace(' ', '_', $naam);
$naam = clean($naam);

$thema = $thema . '/';

$ext_array = explode(',', $extensions);

// Create path
$basepath = $modx->config['base_path']; // Site root
$target_path = $basepath . $path; // root /assets/upload

// Get Filename and make sure its good.
$filename = basename($_FILES['image']['name']);

// Get files extension
$ext = pathinfo($filename, PATHINFO_EXTENSION);
//make lowercase for comparison
$ext = strtolower($ext);

if ($filename != '') {
    // Make filename a good unique filename.
    // Make lowercase
    $filename = mb_strtolower($filename);
    // Replace spaces with _
    $filename = str_replace(' ', '_', $filename);
    // Add timestamp
    $filename = date("Ymdgi") . '_' . $filename;
    // Add name
    $filename = $naam . '_' . $filename;

    // Set final path
    $target_path = $target_path . $thema . $filename;
    if ($_FILES['image']['size'] > $minsize) {
        if ($_FILES['image']['size'] < $maxsize) {
            if (in_array($ext, $ext_array)) {
                if (move_uploaded_file($_FILES['image']['tmp_name'], $target_path)) {
                    // Upload successful
                    $hook->setValue('image', $filename);
                    return true;
                } else {
                    // File not uploaded
                    $errorMsg = 'Er is een fout opgetreden, kan image niet uploaden';
                    $hook->addError('image', $errorMsg);
                    return false;
                }
            } else {
                // File type not allowed
                $errorMsg = 'Dit image is niet in JPEG of TIFF formaat';
                $hook->addError('image', $errorMsg);
                return false;
            }
        } else {
            //filesize to big
            $errorMsg = 'image mag niet groter zijn dan 7MB ';
            $hook->addError('image', $errorMsg);
            return false;
        }
    } else {
        //filesize too low
        $errorMsg = 'image mag niet kleiner zijn dan 2MB';
        $hook->addError('image', $errorMsg);
        return false;
    }
}
$hook->setValue('image', $filename);
return true;