Variables in PHP are represented by a dollar sign followed by the name of the variable. The variable name is case-sensitive.
Variable names follow the same rules as other labels in PHP. A valid variable name starts with a letter or underscore, followed by any number of letters, numbers, or underscores. As a regular expression, it would be expressed thus:
For information on variable related functions, see the Variable Functions Reference.
$var = 'Bob';
$Var = 'Joe';
echo "$var, $Var"; // outputs "Bob, Joe";
$4site = 'not yet'; // invalid; starts with a number
$_4site = 'not yet'; // valid; starts with an underscore
$täyte = 'mansikka'; // valid; 'ä' is (Extended) ASCII 228.