Which Form Enctype To Use?

Question

Q1A. Do I need to add "enctype=" on my following keyword search form that posts to the same page ?

Q1B. Is it really necessary to add enctype ? The form processor will be in php.

Q1C. Notice the "action=". Does it make any difference if the "action=" contains a url that has been urlencode() or not ?

<form method='POST' name='search' id='search' action="<?php echo htmlspecialchars($_SERVER['PHP_SELF']).'?tbl='.urlencode($tbl).'&col='.urlencode($col).'&page='.urlencode($page);?>">
    <label for='url'>Url</label><br>
    <input type='url' name='url' id='url' maxlength="100" required><br>
    <label for='anchor'>Anchor</label><br>
    <input type='text' name='anchor' id='anchor' required><br>
    <label for='anchor'>Username</label><br>
    <input type="text" pattern="[a-zA-Z0-9]{5,8}" title="Type 5 to 8 alphanumeric characters">
    <label for='email'>Email</label><br>
    <input type='email' name='email' id='email' maxlength="100" required><br>

Q1D. Is it really necessary to add enctype if the form was submitting to another page on same domain/website via POST method ?

Q2. If I use "application/x-www-form-urlencoded" then would this be a doule urlencoding in any way since I have already urlencoded the destination url ?

<form method='POST' name='search' id='search' action="<?php echo htmlspecialchars($_SERVER['PHP_SELF']).'?tbl='.urlencode($tbl).'&col='.urlencode($col).'&page='.urlencode($page);?>">

Q3. If I use:

<form method='POST' name='search' id='search' action="<?php echo htmlspecialchars($_SERVER['PHP_SELF']).'?tbl='.urlencode($tbl).'&col='.urlencode($col).'&page='.urlencode($page);?>">"

Then would I have to decode the submitted data on the serverside or what ?

Q4. Anything else I need to know ?

Answer 1

Do I need to add "enctype=" on my following keyword search form that posts to the same page ?

Only if you want a non-default value for it. Which you probably don't want to do unless you are using a file input.

Q1C. Notice the "action=". Does it make any difference if the "action=" contains a url that has been urlencode() or not ?

The URL may or may not be valid.

Q1D. Is it really necessary to add enctype if the form was submitting to another page on same domain/website via POST method ?

Submitting to another page on the same domain makes absolutely no difference as to if you should specify enctype or not.

Q2. If I use "application/x-www-form-urlencoded" then would this be a doule urlencoding in any way since I have already urlencoded the destination url ?

The attribute describes how the request body will be encoded. It does nothing to the URL.

Q3. If I use ... Then would I have to decode the submitted data on the serverside or what ?

No. PHP will decode query string parameters when populating $_GET.