What does <form action="?"> do when sending to self? [duplicate]

Question

I am following php mysql novice to ninja:

form template below

<form action="?" method="post">
    <div>
        <label for="joketext">Type your joke here:</label>
        <textarea id="joketext" name="joketext" rows="3" cols="40"></textarea>
    </div>
    <div><input type="submit" value="Add"></div>
</form>

Part of the PHP controller:

if(isset($_POST['joketext'])) //insert block
{
    try
    {                     //prepared starement
        $sql = 'INSERT INTO joke SET 
            joketext = :joketext,
            jokedate = CURDATE()';

What does the '?' do in the form action

Answer 1

? is used to separate the URL path from the query string. In this case, the query string is empty, so it's the same as if it had been action="".

However, there's a difference. If the original page was loaded using a URL that had a query string, action="" will submit the form with that same query string. Putting an explicit ? in the URL replaces the original query string with this empty one.

Answer 2

It uses the current URL with an empty query string as the action of the form. An empty query string which means no query string at all.

Answer 3

That way the form will post the data to a location "?", If your file contains the PHP code you won't need any action="?" You can remove it, the form will post to it self and replace isset($_POST["joketext"]) with isset($_POST["submit"]) to detect the submit button that have been clicked not the joketext exist

it will be like this
HTML:

<form method="post">
<div>
    <label for="joketext">Type your joke here:</label>
    <textarea id="joketext" name="joketext" rows="3" cols="40"></textarea>
</div>
<div><input type="submit" name="submit" value="Add"></div>

PHP:

if(isset($_POST['submit'])) //insert block
 {
  try
   {                     //prepared starement
    $sql = 'INSERT INTO joke SET 
        joketext = :joketext,
        jokedate = CURDATE()';