PHP File Redirection 404 Error

https://bdeas.com/marketplace

make new directory “marketplace” and put mk.php there.

Then it doesn’t load in the original page that calls the php but,
https://bdeas.com/marketplace
but just shows the directory.

I need a way to place the php file or call the php file so that when /marketplace needs it, I can give it.

If you put in root directory where wordpress installed,
how about:

<form action=”<?php ABSPATH ?>/mk.php” method=”get”>

It will goes to: https://bdeas.com/mk.php

I get a Oops! That page can’t be found.
It looks like nothing was found at this location. Maybe try one of the links below or a search? error again.

This was where it redirected to https://bdeas.com/marketplace/%3C?link=test&submit=Send

Still /marketplace.

This was what I used. <form action="<?php ABSPATH ?>/mk.php" method="get">

Put it the theme root and try this:

<form action="<?php get_stylesheet_directory_uri() . '/mk.php'; ?>" method="GET">

An even better way would be the following:
In template:

<form action="" method="get">
  <input type="hidden" name="jiungusa_form_nonce" value="<?php echo wp_create_nonce('jiungusa_form_nonce');?>">

<!-- Rest of Form -->
</form>

In functions.php

add_action( 'init', function() {
  if( ! empty( $_REQUEST['jiungusa_form_nonce'] ) ) {
    require_once( 'mk.php' );
  }
});

What do you mean by “theme root” and “in template”

I get functions.php but I don’t get the rest.

The theme root is where you theme functions.php, index.php, and style.css are. The template is where you place the <form> code.