$message is used to store variable data. $$message can be used to store variable of a variable. Data stored in $message is fixed while data stored in $$message can be changed dynamically.
$var1 = ‘Variable 1’
This can be interpreted as $ Variable 1=‘variable2’;
For me to print value of both variables, I will write
Explain the difference between $message and $$message in PHP
$message is a variable and $$message is a variable of another variable.
$Message = "Query";
$Query = “Home";
echo $message //Output:- Query
echo $$message //output :-Home
$$message allows the developer to change the name of the variable dynamically.