Essential PHP S&S Elements

Описание: Variable Variables ( $$ ) :
PHP supports variable variables, which means that the name of a variable can be dynamic. Using $$name , if $name = "foo" , then $$name refers to the variable $foo . This can be useful in certain meta-programming scenarios, but should be used carefully to maintain code clarity.

$varName = "color";
$$varName = "red"; // creates $color variable with value "red"
echo $color; // Outputs: red
echo $$varName; // Outputs: red (same as $color)