Errors don’t happen out of nowhere. When does the error appear? When did it start? What version of Atom and your OS are you running? How long ago did you install PHP 7? Have you used
ide-php, specifically? When did you download
ide-php? What happens when you open the command line and type
php -v? What happens when you use a terminal package or
process-palette to execute
php -v from within Atom?