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

My version not relying on grep.

First parameter (mandatory): group
Second parameter (optional, defaults to current user)

isInGroup(){
   group="$1"
   user="${2:-$(whoami)}"
   ret=false 
   for x in $(groups "$user" |sed "s/.*://g")
   do [[ "$x" == "$group" ]] && { ret=true ; break ; }
   done
   eval "$ret"
}