This Zen Cart article discusses the factors that go into the maximum size file you can upload to your web server. There are several factors that influence this, and we will go over these now.
By default, most web hosting companies set up webservers so that the maximum size for PHP uploads is 2 MB. In order to change this figure, you must have access to the php.ini file. Some webhosts give their customers access to this file, while others do not.
Internet connection speed also has some impact on the upload process, specifically affecting the time it takes for files to upload. Since PHP is only allowed to wait a certain length of time for an action to complete, you may encounter some difficulties when attempting to upload larger files if the set time limit is too short. This time limit can be changed though. Again, you will need access to the php.ini file, where you can change the ‘max_execution_time’, and ‘max_input_time’ values to increase the time limit.
There are also file upload size limits in zen cart that operate independently of the restrictions set by your web host. These limits can be modified in your Zen Cart Admin. To change them, navigate to Configuration–> Maximum Values, and find the ‘Maximum Upload Size’ parameter. The number in this field(in bytes) is the maximum file upload size that zen cart will accept. If you attempt to upload a file exceeding this limit, zen cart will reject it. It should be noted that this number is ignored if the PHP limits in the php.ini file are smaller, as PHP will reject the upload before Zen Cart can check it using the values found in the Maximum values area if the file is too large.