从Ajax访问私有静态类属性

Question

I have a class similar to this:

class My_Class {
    private static $array = null;
    private static $another_array = null;

    private function __construct() {
        self:$another_array = array( 'data' );
    }

    // This gets executed from jQuery Ajax when user clicks a button
    public static function process_ajax() {
        self::generate_html();
    }

    private static function generate_html() {
        if ( ! self::$array ) {
            self::$array = array( 'some data' );
        }
    }

    // This gets executed when user is trying to save Ajax generated form
    public static function save_ajax_form() {
        print_r( self::$another_array ); // prints [0] => 'data'
        self::validate_data();
    }

    private static function validate_data() {
        // WHY DOES THIS EVALUATE TRUE? 
        if ( ! is_array( self::$array ) ) {

        }

    }
}

How can I access My_Class::$array property from an Ajax call?

Answer 1

Even though you are declaring the variable static it is going to be initialized to null on every request - PHP is "stateless" in this way, static variables will not persist accross requests. Since you do want to persist the value you will need to use something like $_SESSION, APC or memcached to hold the value of $array.

When your ajax calls save_ajax_form() it immediately then calls validate_data(). The $array variable is still initialized to null since the call to generate_html() happened in a different request, so the check to see if it is not an array will return true.

See: Does static variables in php persist across the requests?