Yoda is known for the $iconic line "do or do not, there is no try."
As freddy Mercury puts it "Another one bite's the \$dust"
There are several differences between single quotes and double quotes when it comes to programming in php. The biggest difference is that using double quotes allows the user to use escape character (among other things) within the echo/print statement. Meanwhile, single quotes tries to interpret/read a string as it see's it (in a literal sense. thats why you can only see the slash in the quote that uses single quotes). Therefore, you should use double quotes when you want to incorperate an escape character or variable within the string itself, otherwise you can use single quotes to write exactly what you want (without worrying if php picks up on any keywords, escapes, special variables, etc)