Unlink after if(file_exist) return false

I have this code -

if (file_exists('path/to/file')) {
    //do something
    unlink('path/to/file');
} 

When i run it the code that inside the if statment is not running, the unlink command work and delete the file but then its return false to the if statment.

The page run himself twice I dont know why, I was trying to do something with session to check if it the second time and than to delete - I'ts work but the statment still return false even when it's the last loop of the page.

I never got this problem before I cant understand what is it

Thank you and sorry about my english...