I inserted the following code, see below, to have a post submitted from the front-end. When you submit it, this warning appears:

Warning: array_filter() expects parameter 1 to be an array, string given in [...]/wp-includes/post.php on line 3148

And I can't figure out where the warning come from, which array is a string?

function ty_front_end_form() {

    <form id="custom-post-type" name="custom-post-type" method="post" action="">

    <p><label for="title">Post Title</label><br />

    <input type="text" id="title" value="" tabindex="1" size="20" name="title" />


    <p><label for="description">Post Description</label><br />

    <textarea id="description" tabindex="3" name="description" cols="50" rows="6"></textarea>


    <p><?php wp_dropdown_categories( 'show_option_none=Category&tab_index=4&taxonomy=category' ); ?></p>

    <p><label for="post_tags">Post Tags</label>

    <input type="text" value="" tabindex="5" size="16" name="post-tags" id="post-tags" /></p>

    <p align="right"><input type="submit" value="Publish" tabindex="6" id="submit" name="submit" /></p>

    <input type="hidden" name="post-type" id="post-type" value="custom_posts" />

    <input type="hidden" name="action" value="custom_posts" />

    <?php wp_nonce_field( 'name_of_my_action','name_of_nonce_field' ); ?>




function ty_save_post_data() {

    if ( empty($_POST) || !wp_verify_nonce($_POST['name_of_nonce_field'],'name_of_my_action') )
       print 'Sorry, your nonce did not verify.';



        // Do some minor form validation to make sure there is content
        if (isset ($_POST['title'])) {
            $title =  $_POST['title'];
        } else {
            echo 'Please enter a title';
        if (isset ($_POST['description'])) {
            $description = $_POST['description'];
        } else {
            echo 'Please enter the content';

        $tags = $_POST['post_tags'];
        $tags = "";

        // Add the content of the form to $post as an array
        $post = array(
            'post_title' => wp_strip_all_tags( $title ),
            'post_content' => $description,
            'post_category' => $_POST['cat'],  // Usable for custom taxonomies too
            'tags_input' => $tags,
            'post_status' => 'draft',           // Choose: publish, preview, future, etc.
            'post_type' => 'listings'  // Use a custom post type if you want to
        wp_insert_post($post);  // http://codex.wordpress.org/Function_Reference/wp_insert_post

        $location = home_url(); // redirect location, should be login page 

        echo "<meta http-equiv='refresh' content='0;url=$location' />"; exit;
    } // end IF

  • You should always add the code, if is necessary for the question. If users read it later and the external link is broken is the q/a not helpful. – bueltge Dec 13 '17 at 13:19

If you check the line from the error notice you should find in WP 4.9.1 the usage of the function array_filter, that need a array as parameter (see the code). Your value inside your array for an post need an array for 'post_category', is currently a string.

From the source of the WP core:

* @type array  $post_category         Array of category names, slugs, or IDs.
*                                     Defaults to value of the 'default_category' option.

In your source example you should change this and it should work, 'post_category' => array( $_POST['cat'] ),.

// Add the content of the form to $post as an array
$post = array(
    'post_title' => wp_strip_all_tags( $title ),
    'post_content' => $description,
    'post_category' => array( $_POST['cat'] ), // Usable for custom taxonomies too
    'tags_input' => $tags, // Need an array
    'post_status' => 'draft', // Choose: publish, preview, future, etc.
    'post_type' => 'listings', // Use a custom post type if you want to
wp_insert_post( $post );
  • 1
    also tags_input is array for the tags probably better use explode with comma to accept more than 1 tag – Shibi Dec 13 '17 at 13:31

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