PHP Variable Scope Superglobal variables


Superglobal variables are defined by PHP and can always be used from anywhere without the global keyword.


function getPostValue($key, $default = NULL) {
    // $_POST is a superglobal and can be used without
    // having to specify 'global $_POST;'
    if (isset($_POST[$key])) {
        return $_POST[$key];

    return $default;

// retrieves $_POST['username']
echo getPostValue('username');

// retrieves $_POST['email'] and defaults to empty string
echo getPostValue('email', '');