Form element name – array type is not working

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Why the ?pgggo-taxon-select%5B%5D=14&pgggo-taxon-select%5B%5D=1 in the URL

There are three common reasons why would one see that upon submitting the form:

  1. The form’s method is post (which corresponds to the HTTP POST method) and either:

    a) The current page indeed has that string in the URL. E.g. You’re on example.com/my-page/?pgggo-taxon-select%5B%5D=14&pgggo-taxon-select%5B%5D=1

    b) The form’s action has that string. E.g. <form action="/my-app?pgggo-taxon-select%5B%5D=14&pgggo-taxon-select%5B%5D=1">

  2. Or (most likely in your case), the form’s method is get (which corresponds to the HTTP GET method, and get is the default form method).

Okay, but why not ?pgggo-taxon-select[]=14&pgggo-taxon-select[]=1 ?

Because special characters like square brackets ([ and ]) (that have specific meaning) in URLs need to be percent-encoded/URL-encoded (more details on MDN or Wikipedia); hence, those brackets become %5B and %5D respectively in the URL — try urlencode( '[' ) in PHP.

So don’t worry.. all is good.

PHP would still treat the input ($_GET['pgggo-taxon-select']) — when sent as pgggo-taxon-select%5B%5D via the GET method — as an array. In fact, PHP (or the server) may not be able to properly parse the input if it was using the unescaped [ and ].

From your comment (formatted for brevity), “but post method does not add any query string but I still get the required array. Can I use a post ? Is it recommended?“:

Just use the method that better fits the form’s context/purposes — if it’s for uploading a file, you should use post; if it’s just to read/display posts filtered by certain criteria, you can just use get.

And these resources would help you understand when to use what HTTP method in submitting a form: