$nb_students = 7;
echo 'Our group contains $nb_students students';
echo "Our group contains $nb_students students";
echo 'These apples cost $2 per kilogram';
echo "These apples cost $2 per kilogram";
echo "Today's our lucky day";
echo 'Today's our lucky day';
echo "This is what we call "bad luck"";
echo 'This is what we call "bad luck"';
echo 'This week\'s been our "honey moon"';