About PHP get post parameters

First Contact PHP things, want to ask, I front-end HTML, with get submitted data, the address bar is like this:
..../.. &a=good_1&b=200&a=good_2&b=300&a=good_4&b=400

Use $_get to get parameter values in PHP files, using foreach ($_request as $key = = $value)
But can only get to the last one, namely a=good_4&b=400, the other two get not to, this How to solve?

Reply to discussion (solution)

Your key is repeated.

Because the URL parameter string violates the PHP convention (the incoming variable with the same name is in the form of an array), it cannot be taken
You can parse it yourself from $_server[' query_string '.

This is not a key duplication problem.
..../.. &a[]=good_1&b[]=200&a[]=good_2&b[]=300&a[]=good_4&b[]=400
This will be desirable to the value

Your key is repeated.

Your reference field except A is B ah, obviously repeated

The parameters are repeating.

The name of the parameter is repeated, of course it will be overwritten.

&a=good_1&b=200 &a=good_2&b=300 &a=good_4&b=400
The parameters are repeated and will of course be overwritten at the end. You can use an array to pass or change the parameter name.
For example:
&a[]=good_1&b[]=200&a[]=good_2&b[]=300&a[]=good_4&b[]=400

Array (    [0] = Good_1    [1] = Good_2    [2] = good_4) Array (    [0] =    [1]    + [2] = 400)

Because the URL parameter string violates the PHP convention (the incoming variable with the same name is in the form of an array), it cannot be taken
You can parse it yourself from $_server[' query_string '.

Moderator is such as and to PHP understand so thin oh???

