PHP and WHMCS
Your PHP configuration is extremely important for successfully running WHMCS.
For more information about PHP and WHMCS, see:
500 Internal Server Error
The 500 internal server error indicates there is a problem processing the request. This is usually due to a customisation or an issue with the PHP configuration causing issues.
To troubleshoot this, begin by adding $display_errors = true; to your configuration.php file or reviewing the PHP error_log file.
This should indicate which file is causing the error. If it is a third-party module or customization, remove the custom files and confirm if this resolves the error.
Maximum Execution Time
By default, WHMCS enforces a max_execution_time limit of 300 seconds for general requests.
If this limit is too low for a specific task or operation, you may see the following error:
PHP Fatal error: Maximum execution time of 300 seconds exceeded in /path/to/file.php
Increasing the max_execution_time
To override the max execution time limit and increase it to a higher value, add the following line to your WHMCS configuration.php file:
$overidephptimelimit = 500;