wp_insert_post not adding category - wordpress

Question

I'm building a WordPress theme where people can submit posts using wp_insert_post. The code below adds the post title but does not add the category specified by the user. Instead it puts it in uncategorized.
How do I get it to add the new category to the post when submitted?
if(isset($_POST['new_post']) == '1') {
$post_title = $_POST['post_title'];
$new_cat_ID = $_POST['category'];
//Checking if category already there
$cat_ID = get_cat_ID( $_POST['newcat'] );
//If not create new category
if($cat_ID == 0) {
$cat_name = array('cat_name' => $_POST['newcat']);
wp_insert_category($cat_name);
}
//Get ID of newly created category
$new_cat_ID = get_cat_ID($_POST['newcat']);
// Create post object
$new_post = array(
'ID' => '',
'post_title' => $post_title,
'post_status' => 'publish',
'post_author' => $user->ID,
'tax_input' => array( 'category' => $new_cat_ID )
);
// Insert the post into the database
$post_id = wp_insert_post($new_post);
// This will redirect you to the newly created post
$post = get_post($post_id);
wp_redirect( home_url() );
exit;
}
Here's the HTML for the form:
<form style="" action="" method="post" id="foo">
<input type="hidden" name="new_post" value="1"/>
<input type="text" name="post_title" value="title" id="input-title"/>
<input type="text" name="category" value="apples" id="category" />
<input type="submit" value="Login">
</form>

Answer 1

The category input should be:
<input type="text" name="newcategory" value="apples" id="category" />
In my tests, wp_insert_category did not work and wp_insert_term had to be used (as per this forum thread).
Your wp_redirect is not taking where you thing it does. The section //This will redirect you to the newly created post is plain wrong.
The following is a working example with a security layer added with wp_nonce_field, but you must add User Input Data Validation.
Also, I'm testing while logged in, so it works. Your code does not take care of $user->ID, research for get_current_user to get this right.
<?php
if ( isset( $_POST['noncename_so_17539370'] ) && wp_verify_nonce( $_POST['noncename_so_17539370'], 'nonce_so_17539370' ) )
{
if( isset($_POST['new_post']) == '1' ) {
//Checking if category already there
$cat_ID = get_cat_ID( $_POST['newcat'] );
//If not create new category
if( !$cat_ID ) {
$arg = array( 'description' => "my description", 'parent' => 0 );
$cat_ID = wp_insert_term($_POST['newcat'], "category", $arg);
}
// Create post object
$new_post = array(
'ID' => '',
'post_title' => $_POST['post_title'],
'post_status' => 'publish',
//'post_author' => $user->ID,
'tax_input' => array( 'category' => $cat_ID )
);
// Insert the post into the database
$post_id = wp_insert_post($new_post);
// This will redirect you to the newly created post
$post = ;
wp_redirect( get_permalink( $post_id ) );
exit;
}
} else {
echo 'ERROR';
}
?>
<form style="" action="" method="post" id="foo">
<?php wp_nonce_field( 'nonce_so_17539370', 'noncename_so_17539370' ); ?>
<input type="hidden" name="new_post" value="1"/>
<input type="text" name="post_title" value="title" id="input-title"/>
<input type="text" name="newcat" value="apples" id="category" />
<input type="submit" value="Login">
</form>