Check if a user is in a group

Question

I have a server running where I use php to run a bash script to verify certain information of a user. For example, I have a webhosting server set up, and in order to be able to

Answer 1

Try doing this :

username=ANY_USERNAME
if getent group customers | grep -q "\b${username}\b"; then
    echo true
else
    echo false
fi

or

username=ANY_USERNAME
if groups $username | grep -q '\bcustomers\b'; then
    echo true
else
    echo false
fi