How can PHP configuration affect the ability to execute shell scripts?

PHP configuration can affect the ability to execute shell scripts by restricting certain functions like `exec()`, `shell_exec()`, or `system()`. To enable the execution of shell scripts, you need to check and adjust the `disable_functions` directive in the php.ini configuration file. Remove the functions related to shell script execution from the `disable_functions` list to allow PHP to execute shell scripts.

// Check if the shell execution functions are disabled
$disabled_functions = ini_get('disable_functions');

// Remove shell execution functions from the disabled functions list
$disabled_functions = str_replace('exec,shell_exec,system', '', $disabled_functions);

// Update the php.ini configuration with the modified disabled functions list
ini_set('disable_functions', $disabled_functions);