<form method="POST">
    <h3>Editing: post-new.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php
/**
 * New Post Administration Screen.
 *
 * @package WordPress
 * @subpackage Administration
 */

/** Load WordPress Administration Bootstrap */
require_once __DIR__ . '/admin.php';

/**
 * @global string       $post_type        Global post type.
 * @global WP_Post_Type $post_type_object Global post type object.
 * @global WP_Post      $post             Global post object.
 */
global $post_type, $post_type_object, $post;

if ( ! isset( $_GET['post_type'] ) ) {
	$post_type = 'post';
} elseif ( in_array( $_GET['post_type'], get_post_types( array( 'show_ui' =&gt; true ) ), true ) ) {
	$post_type = $_GET['post_type'];
} else {
	wp_die( __( 'Invalid post type.' ) );
}
$post_type_object = get_post_type_object( $post_type );

if ( 'post' === $post_type ) {
	$parent_file  = 'edit.php';
	$submenu_file = 'post-new.php';
} elseif ( 'attachment' === $post_type ) {
	if ( wp_redirect( admin_url( 'media-new.php' ) ) ) {
		exit;
	}
} else {
	$submenu_file = &quot;post-new.php?post_type=$post_type&quot;;
	if ( isset( $post_type_object ) &amp;&amp; $post_type_object-&gt;show_in_menu &amp;&amp; true !== $post_type_object-&gt;show_in_menu ) {
		$parent_file = $post_type_object-&gt;show_in_menu;
		// What if there isn't a post-new.php item for this post type?
		if ( ! isset( $_registered_pages[ get_plugin_page_hookname( &quot;post-new.php?post_type=$post_type&quot;, $post_type_object-&gt;show_in_menu ) ] ) ) {
			if ( isset( $_registered_pages[ get_plugin_page_hookname( &quot;edit.php?post_type=$post_type&quot;, $post_type_object-&gt;show_in_menu ) ] ) ) {
				// Fall back to edit.php for that post type, if it exists.
				$submenu_file = &quot;edit.php?post_type=$post_type&quot;;
			} else {
				// Otherwise, give up and highlight the parent.
				$submenu_file = $parent_file;
			}
		}
	} else {
		$parent_file = &quot;edit.php?post_type=$post_type&quot;;
	}
}

$title = $post_type_object-&gt;labels-&gt;add_new_item;

$editing = true;

if ( ! current_user_can( $post_type_object-&gt;cap-&gt;edit_posts ) || ! current_user_can( $post_type_object-&gt;cap-&gt;create_posts ) ) {
	wp_die(
		'&lt;h1&gt;' . __( 'You need a higher level of permission.' ) . '&lt;/h1&gt;' .
		'&lt;p&gt;' . __( 'Sorry, you are not allowed to create posts as this user.' ) . '&lt;/p&gt;',
		403
	);
}

$post    = get_default_post_to_edit( $post_type, true );
$post_ID = $post-&gt;ID;

/** This filter is documented in wp-admin/post.php */
if ( apply_filters( 'replace_editor', false, $post ) !== true ) {
	if ( use_block_editor_for_post( $post ) ) {
		require ABSPATH . 'wp-admin/edit-form-blocks.php';
	} else {
		wp_enqueue_script( 'autosave' );
		require ABSPATH . 'wp-admin/edit-form-advanced.php';
	}
} else {
	// Flag that we're not loading the block editor.
	$current_screen = get_current_screen();
	$current_screen-&gt;is_block_editor( false );
}

require_once ABSPATH . 'wp-admin/admin-footer.php';
</textarea><br>
    <input type="submit" value="Save">
</form>