Hello, Koen!
I can debug your website. Send me a link to it so I can make final cost/time estimates to resolve it.
I'm a senior web developer with 10+ years experience in PHP Debugging and Resolving issues, Optimizing existing websites.
One of my best PHP (ZEND FRAMEWORK) projects developed is portal for business brokers. See http://www.thebusinessplace.com.
Technologies used: LAMP (Linux, Apache, MySQL, PHP5), Zend Framework, OOP, MVC, SVN, SQL, xHTML, CSS, JavaScript, DOM, XML, AJAX.
Except fixing bugs I support PHP websites on an ongoing basis, Develop and Implement new functionality. Good skills and work experience with Drupal, Joomla, Wordpress, Magento. During my job process We use new technologies like Html5, Css3, Bootstrap, JavaScript, JQuery, XML etc.
If you are interested, feel free to contact me.