Form Submission Warning: Cannot modify header error only when plugin is deactivated

Question

I have created some custom post forms that I'm now using in place of a plugin called WP User Frontend which allows you to post and edit from front end. These post forms we're working great but when I deactivated the plugin I now I get a warning when the post completes its' upload saying..

Warning: Cannot modify header information - headers already sent by (output started at /home/####/public_html/#####/wp-content/themes/####/header-default.php:2) in /home/#####/public_html/#####/wp-includes/pluggable.php on line 881.

Now I checked for white spaces and I honestly don't see any in the header, page template, or footer and I don't believe it has anything to with that because the post forms work fine when the plugin is activated. I'm also using buddypress which has a form submit for avatars and that works fine without plugin activated so I'm thinking my form has something missing that the plugin was providing. Instead of pasting the entire code including the html form I'm going to show the php part of the template that does the work.

<?php// Template Name: Album Post Form ?>
<?php get_header(); ?>

<?php if( 'POST' == $_SERVER['REQUEST_METHOD'] && !empty( $_POST['action'] ) &&  $_POST['action'] == "new_post") {
if ( ! function_exists( 'wp_handle_upload' )) {
            require_once(ABSPATH . "wp-admin" . '/includes/image.php');
            require_once(ABSPATH . "wp-admin" . '/includes/file.php');
            require_once(ABSPATH . "wp-admin" . '/includes/media.php');
}
$file=$_FILES;
// Do some minor form validation to make sure there is content
if (isset ($_POST['title'])) {
    $title =  $_POST['title'];
} else {
    echo 'Please enter a game  title';
}
if (isset ($_POST['description'])) {
    $description = $_POST['description'];
} else {
    echo 'Please enter the content';
}
$tags = $_POST['post_tags'];

// Add the content of the form to $post as an array
$new_post = array(
    'post_title'    => $title,
    'post_content'  => $description,
    'tags_input'    => array($tags),
    'post_status'   => 'publish',           // Choose: publish, preview, future, draft, etc.
    'post_type' => fod_albums  // Use a custom post type if you want to
);
//save the new post and return its ID
$pid = wp_insert_post($new_post);
if (!($file['album_image']['name'] == "")) {
  $cover_art_id = media_handle_sideload( $file['album_image'], $pid );
  if ( is_wp_error($cover_art_id) ) {
    @unlink($file_array['tmp_name']);
    return $cover_art_id;
  }
  if(!is_wp_error($cover_art_id)){
   wp_set_object_terms( $cover_art_id, 'cover_art', 'category');
  }
  update_post_meta($pid,'album_cover',$cover_art_id);
} elseif ($file['album_image']['name'] == "" && !($_POST['cover_radio'] == '')) {
  update_post_meta($pid,'music_art',$_POST['cover_radio']);
}
wp_redirect( get_permalink($pid)); 
exit();
} 
do_action('wp_insert_post', 'wp_insert_post');
?>

Any ideas?

Answer 1

You can't do this:

wp_redirect( get_permalink($pid));

after you've already sent content to the browser. Headers were already sent, and wp_redirect is attempting to send a header again. The first three lines of the template you pasted above are all sending content to the browser, when you close and open php. evidently your header.php file is doing the same.

You should hook an action to process your form before the template is loaded.

function wpa63889_process_form( $query ) {
    if ( $query->is_page( 'my-form-page' ) && isset( $_POST['title'] ) ) {
        // process form data
    }
}
add_action( 'pre_get_posts', 'wpa63889_process_form' );