If you are using FastCGI or just switching from other PHP handler to FastCGI, you may get in a 500 Internal Server Error when running/opening a PHP script that runs for 40 or certain/several seconds. For your information, by default, FastCGI process will timeout after 40 seconds so you will get 500 Internal Server Error.

To solve this, you will need to increase FcgidIOTimeout or IPCCommTimeout for older version.

To set this directive via CPanel WHM:

• Open Service Configuration -> Apache Configuration
• Click Include Editor
• Find Pre Main Include, select All Versions
• Insert this to the textarea (set the timeout to 10000 seconds) -> FcgidIOTimeout 10000
• Click Update and restart your Apache

If you don't have WHM, You can also change your httpd.conf to add this code at the top:

FcgidIOTimeout 10000

Then, simply save the changes and restart your apache