How to get source code of external website with use of php script

I would like to get the source code of external website. file_get_contents() shows nothing - false. I need it in order to looking for a specific words then. I mean, when I go to some website, do right-click -> view source code I have the output. And I would like to have the same but via php script - to get the source code and have it as a string to proceed it later on.