Wordpress - Prevent post from being published if custom fields not filled
As m0r7if3r pointed out, there is no way of preventing a post from being published using the save_post hook, since the by the time that hook is fired, the post is already saved. The following, however, will allow you to revert the status without using wp_insert_post_data and without causing an infinite loop.
The following is not tested, but should work.
<?php
add_action('save_post', 'my_save_post');
function my_save_post($post_id) {
if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE )
return;
if ( !isset( $_POST['ep_eventposts_nonce'] ) )
return;
if ( !wp_verify_nonce( $_POST['ep_eventposts_nonce'], plugin_basename( __FILE__ ) ) )
return;
// Is the user allowed to edit the post or page?
if ( !current_user_can( 'edit_post', $post->ID ) )
return;
// Now perform checks to validate your data.
// Note custom fields (different from data in custom metaboxes!)
// will already have been saved.
$prevent_publish= false;//Set to true if data was invalid.
if ($prevent_publish) {
// unhook this function to prevent indefinite loop
remove_action('save_post', 'my_save_post');
// update the post to change post status
wp_update_post(array('ID' => $post_id, 'post_status' => 'draft'));
// re-hook this function again
add_action('save_post', 'my_save_post');
}
}
?>
I've not checked, but looking at the code, the feedback message will display the incorrect message that the post was published. This is because WordPress redirects us to an url where the message variable is now incorrect.
To change it, we can use the redirect_post_location filter:
add_filter('redirect_post_location','my_redirect_location',10,2);
function my_redirect_location($location,$post_id){
//If post was published...
if (isset($_POST['publish'])){
//obtain current post status
$status = get_post_status( $post_id );
//The post was 'published', but if it is still a draft, display draft message (10).
if($status=='draft')
$location = add_query_arg('message', 10, $location);
}
return $location;
}
To summarise the above redirect filter: If a post is set to be published, but is still a draft then we alter the message accordingly (which is message=10). Again, this is untested, but should work. The Codex of the add_query_arg suggests that when a variable is already it set, the function replaces it (but as I say, I haven't tested this).
OK, this is finally how I ended up doing it: an Ajax call to a PHP function that does the checking, sort of inspired by this answer and using a clever tip from a question I asked on StackOverflow. Importantly, I make sure that only when we want to Publish the checking is done, so that a Draft can always be saved without the checking. This ended up being the easier solution to actually prevent the publication of the post. It might help someone else, so I wrote it up here.
First, add the necessary Javascript:
//AJAX to validate event before publishing
//adapted from https://wordpress.stackexchange.com/questions/15546/dont-publish-custom-post-type-post-if-a-meta-data-field-isnt-valid
add_action('admin_enqueue_scripts-post.php', 'ep_load_jquery_js');
add_action('admin_enqueue_scripts-post-new.php', 'ep_load_jquery_js');
function ep_load_jquery_js(){
global $post;
if ( $post->post_type == 'event' ) {
wp_enqueue_script('jquery');
}
}
add_action('admin_head-post.php','ep_publish_admin_hook');
add_action('admin_head-post-new.php','ep_publish_admin_hook');
function ep_publish_admin_hook(){
global $post;
if ( is_admin() && $post->post_type == 'event' ){
?>
<script language="javascript" type="text/javascript">
jQuery(document).ready(function() {
jQuery('#publish').click(function() {
if(jQuery(this).data("valid")) {
return true;
}
var form_data = jQuery('#post').serializeArray();
var data = {
action: 'ep_pre_submit_validation',
security: '<?php echo wp_create_nonce( 'pre_publish_validation' ); ?>',
form_data: jQuery.param(form_data),
};
jQuery.post(ajaxurl, data, function(response) {
if (response.indexOf('true') > -1 || response == true) {
jQuery("#post").data("valid", true).submit();
} else {
alert("Error: " + response);
jQuery("#post").data("valid", false);
}
//hide loading icon, return Publish button to normal
jQuery('#ajax-loading').hide();
jQuery('#publish').removeClass('button-primary-disabled');
jQuery('#save-post').removeClass('button-disabled');
});
return false;
});
});
</script>
<?php
}
}
Then, the function that handles the checking:
add_action('wp_ajax_ep_pre_submit_validation', 'ep_pre_submit_validation');
function ep_pre_submit_validation() {
//simple Security check
check_ajax_referer( 'pre_publish_validation', 'security' );
//convert the string of data received to an array
//from https://wordpress.stackexchange.com/a/26536/10406
parse_str( $_POST['form_data'], $vars );
//check that are actually trying to publish a post
if ( $vars['post_status'] == 'publish' ||
(isset( $vars['original_publish'] ) &&
in_array( $vars['original_publish'], array('Publish', 'Schedule', 'Update') ) ) ) {
if ( empty( $vars['_start_date'] ) || empty( $vars['_end_date'] ) ) {
_e('Both Start and End date need to be filled');
die();
}
//make sure start < end
elseif ( $vars['_start_date'] > $vars['_end_date'] ) {
_e('Start date cannot be after End date');
die();
}
//check time is also inputted in case of a non-all-day event
elseif ( !isset($vars['_all_day'] ) ) {
if ( empty($vars['_start_time'] ) || empty( $vars['_end_time'] ) ) {
_e('Both Start time and End time need to be specified if the event is not an all-day event');
die();
}
elseif ( strtotime( $vars['_start_date']. ' ' .$vars['_start_time'] ) > strtotime( $vars['_end_date']. ' ' .$vars['_end_time'] ) ) {
_e('Start date/time cannot be after End date/time');
die();
}
}
}
//everything ok, allow submission
echo 'true';
die();
}
This function returns true if everything is fine, and submits the form to publish the post by the normal channel. Otherwise, the function returns an error message that is shown as an alert(), and the form is not submitted.
I think that the best way to go about this is not to PREVENT the status change from happening so much as it is to REVERT it if it does. For example: You hook save_post, with a really high priority (so that the hook will fire very late, namely after you do your meta insert), then check the post_status of the post that's just been saved, and update it to pending (or draft or whatever) if it doesn't meet your criteria.
An alternate strategy would be to hook wp_insert_post_data to set the post_status directly. The disadvantage to this method, as far as I'm concerned, is that you will not have inserted the postmeta into the database yet, so you will have to process it, etc in place to do your checks, then process it again to insert it into the database...which could become a lot of overhead, either in performance or in code.