How to troubleshoot when PHP exec is not working as expected?

To address the issue of PHP exec function not working, you can try the following steps:

1. Check the PHP configuration file to make sure that the safe mode is not enabled and that the exec function is not disabled in the list of disabled functions.
2. Check permissions: Ensure that the PHP script has the necessary permissions to execute the exec function. If the script is located in the web server’s directory, make sure that the directory and its subdirectories can be accessed by the PHP process.
3. Check the executable file path: Make sure that the path of the executable file being executed in the exec function is correct, and that the PHP process has the permission to execute that executable file.
4. Check system restrictions: Some systems may limit the execution of the exec function, such as SELinux or AppArmor. In this case, you will need to adjust the system configuration or disable these restrictions.
5. Check the return value and error message: Use the return value and error message of the exec function for debugging purposes. You can capture the error message by passing a second argument to the exec function.
6. When executing commands, try to use absolute paths to avoid issues caused by different environment variables.

If the above steps do not solve the problem, it may be due to other reasons causing the exec function to not work. You can try using alternative functions or tools to execute your command, such as shell_exec or system function, or use a different programming language or tool to perform specific operations instead of the exec function.