PHP manual:
...
post_max_size integer
Sets max size of post data allowed. This setting also affects file upload. To upload large files, this value must be larger than upload_max_filesize. If memory limit is enabled by your configure script, memory_limit also affects file uploading. Generally speaking, memory_limit should be larger than post_max_size. ...
One must set post_max_size > upload_max_filesize. This is a PHP configuration which needs to be in place before uploads will work correctly / as expected. The POST needs space to accommodate all information sent via POST including: product id, attribute, quantity, all uploaded files in the same form, etc (all these must fit inside post_max_size).
Fixing this is critical if you want to allow larger uploaded files via PHP.
Note: Some HTTP(S) daemons also limit the post size (so the hosting provider may need to the configuration of these as well to ensure end users can upload larger files).
Justin G:
... I am using ZC V1.5.0, PHP version 5.4.39 ...
Note: Zen Cart 1.5.0 is past End of Life (reached on 19 March 2013). Zen Cart 1.5.0 is not fully compatible with PHP 5.4 out-of-box.
While this may not be the cause of the issue in the first post, I would take action on this item quickly.
I would ask the host to temporarily downgrade to PHP 5.3. Afterwards I would start rebuilding / upgrading the store to the current version of Zen Cart. When done with the rebuild / upgrade (and deployment of the next version), have the host switch back to PHP 5.4+.
New versions also include bugfixes, enhancements, compatibility fixes, security patches, etc. Always better to upgrade on your timetable, before things break and customers get upset.
Note: Many here recommend only installing Zen Cart from the distribution available from zen-cart.com. While third party "repackages" and "installers" (such as softaculous) work, the Zen Cart code in third party distributions may contain modifications. And unless you know EVERY way the third party version differs from the stock version available on zen-cart.com, it will be more difficult to obtain help here on the Zen Cart forums.
Justin G:
... I do have my errors set for if the upload fails to display "image not uploaded" ...
I am not aware of this option in a stock Zen Cart installation... When testing, a stock Zen Cart installation will just silently continue when the upload fails (w/o adding the attribute or issuing a 404).
Where are you setting this option? Have you installed a 3rd party Zen Cart module (or modified the add to cart process)? Was the store upgraded from a previous version of Zen Cart? How does the store differ from a stock version of Zen Cart 1.5.0? What is the URL displayed in the browser window? What does FireBug (or other developer tools) show as the HTTP status / code?
Note: I am unable to duplicate the issue in the first post under a stock installation of Zen Cart 1.5.0, 1.5.1, or 1.5.4 (Server: Linux 3.2, PHP 5.4.39, MySQL 5.5.41).
The glass is not half full. The glass is not half empty. The glass is simply too big!
Where are the Zen Cart Debug Logs? Where are the HTTP 500 / Server Error Logs?
Zen Cart related projects maintained by lhûngîl : Plugin / Module Tracker