fix PHP site for 30MB uploads

I have a wordpress site that uses the Platform theme. There is a section of the site that is PHP. It was developed by a developer I found on Freelancer. It was built so that I can upload zip files which automatically create pages that my clients can visit to download the files through. The average size of these zip files is 25-30MB. The PHP section of the site was working seamlessly together for a couple of years, then suddenly one day the PHP site would no longer allow me to upload zip files larger than 12MB. The developer no longer wishes to maintain the site, so I need someone to fix the PHP so that I can upload files of around 30MB. I have contacted my host Godaddy, who has confirmed that my permissions are set to allow uploads of 125MB, with the longest timeout possible, so it seems the problem is not on their end. However, the worker who I award this project to will probably have to call Godaddy using my account details to resolve this issue. Please also be aware I will only award the payment after the site proves to be in working order for three days after the fix, as I recently hired a worker to fix this, but shortly after I awarded him his money, his work broke down and the site went back to broken. I will also need you to keep an eye on the site's main page [login to view URL], as sometimes alterations to the PHP interferes with the main site's Wordpress theme.