PHP Interview Questions and answers

What is the difference between $message and $$message?

$message is a variable and it’s name is “$message”. But $$message is a variable of a variable, in which it is referred by the value of the $message variable itself.

What is the best way to determine if a variable is exiting or not?

isset($x) can be used. But if it’s defined like this
$x=NULL
The answer will be false even if the variable is completely valid.