You can create a custom php.ini file to customize your php configurations.
If you are getting 500 internal server error, please create a file php.ini in your public_html folder and enter the following line:
If you are getting same error under wp-admin login page then copy your php.ini file under wp-admin/ directory and check once again.
Advantages of Su-php is as following :-
suPHP provides an additional protection on servers. It causes php scripts to run under the account username instead of the user ‘nobody’ which is the user that apache/php would run under on a server that is not running suPHP. This feature allows us to track more easily any potential security breaches that come in via insecure php script(s) that a user is running.
suPHP also takes away the requirement of using 777 permissions on directories/files that need write permission. In fact if a directory and/or file has the permission set to (CHMOD) 777 and it is accessible via a browser, then an internal server error 500 will be generated. The highest level of permissions that a user can use on a suPHP enabled server is 755. This permission setting is sufficient enough for any directories/files that needs to be written to.
Please note that suPHP does not allow permissions 666 and 777