What does...

In PHP, the $$ symbol is used to create a variable variable. It allows you to use the value of a variable as the name of another variable. Here's how it works:

1. When you have a variable that contains the name of another variable, you can use $$ to access the value of that variable.

2. For example, if you have a variable $foo that contains the string "bar", then $$foo is equivalent to $bar.

Here's an example:

$foo = "bar";
$$foo = "baz";

echo $foo;     // Output: bar
echo $bar;     // Output: baz
echo $$foo;    // Out...