wp_insert_user not returning anything

Question

I'm using Wordpress 4.5.3, when I call wp_insert_user, it works, user gets created normally, but it does not return the ID or even an error.

Test.php

$userdata = array(
    'user_login' => esc_attr($this->username),
    'user_email' => esc_attr($this->email),
    'user_pass' => esc_attr($this->password),
    'first_name' => esc_attr($this->first_name),
    'display_name' => esc_attr($this->tagline)
);
echo "Test 1";
$register_user = wp_insert_user($userdata);
echo "Test 2"; //This does not echo. Script stops running?

I then opened wp-includes/user.php and edited this:

$user = new WP_User( $user_id );

$meta = apply_filters( 'insert_user_meta', $meta, $user, $update );

foreach ( $meta as $key => $value ) {
    update_user_meta( $user_id, $key, $value );
}

foreach ( wp_get_user_contact_methods( $user ) as $key => $value ) {
    if ( isset( $userdata[ $key ] ) ) {
        update_user_meta( $user_id, $key, $userdata[ $key ] );
    }
}

if ( isset( $userdata['role'] ) ) {
    $user->set_role( $userdata['role'] );
} elseif ( ! $update ) {
    $user->set_role(get_option('default_role'));
}
wp_cache_delete( $user_id, 'users' );
wp_cache_delete( $user_login, 'userlogins' );

if ( $update ) {
    do_action( 'profile_update', $user_id, $old_user_data );
} else {
    return $user_id; // I ADDED THIS FOR TEST PURPOSES. IT WORKS, IT RETURNS THE ID
    do_action( 'user_register', $user_id );
}

return $user_id; // THIS IS WHERE IT SHOULD RETURN THE ID

I made it work editing users.php, but I didn't want to mess with the core to avoid problems when updating my Wordpress site.

Can anyone confirm if this is a bug, or I'm doing something wrong?

Answer 1

I found out what it was.

I had an action hook for user_register on my functions.php. This action hook would automatically login the user after registration. After removing it, it worked.

As requested, the hook was interfearing because I was already logged in. The hook would use wp_set_current_user($user_id); wp_set_auth_cookie($user_id); to log in after registration.