The iframe tag implements form submission without page refresh (no js required) --- parsing

Let’s look at a piece of code first (PHP example)

1. Form code (form.php)

2. Action code (formAction.php):

alert('test....');"; ?>

OK, the above code is very simple, but it realizes form submission without any problem. Refresh....Why is this?

Oh~ In fact, a very basic thing... is the attribute problem of the form tag... as shown in the picture:

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