PHP file to string [duplicate]

This question is an exact duplicate of:

• How can I read a php file into a string using php? 2 answers

Basically I want to run a PHP file from another PHP file to get the output as a string. I also want to be able to pass variables into it.

For example:

$result = get_output('./otherfile.php', $vars);

I have no idea how to do it. any help would be really appreciated.