Php basic questions, session variable array, please give pointers

Php basic questions, session variable array, please give pointers

If ($ new) {// new item selected if (! Isset ($ _ SESSION ['cart']) {$ _ SESSION ['cart'] = array (); // $ _ SESSION ['items '] = 0; $ _ SESSION ['total _ price'] = '0. 00';} if (isset ($ _ SESSION ['cart'] [$ new]) // What does this sentence mean ?? $ New is an input parameter, which is an isbm code of a book, 9787111262817. what does $ _ SESSION ['cart'] [$ new] mean ?? What results will this produce? Can you describe it in detail. Thanks to ing... $ _ SESSION ['cart'] [$ new] ++; else $ _ SESSION ['cart'] [$ new] = 1;

Reply to discussion (solution)

?? Can you understand it ??
$ New = 'a ';
$ _ SESSION ['cart'] = array (
'A' => 'XXX ',
);