How to save a file with UTF-8 encoding and no BOM using PHP?

I am trying to have a file that I generated with PHP saved as UTF-8 without the BOM (Byte Order Mark). Does PHP do anything like this? I am a beginner with PHP, but very technically experienced otherwise. I'm talking about the FILE encoding here -just to be clear. e.g. fopen("what_ever_file", "a+") now I want PHP save the file itself with UTF-8 encoding, NOT system default. I have searched for hours to find an answer, but have not found any info on the subject. Does PHP have any ability to create a text file saved in UTF-8 encoding??