Title Duplication Warning WordPress

Onur YILMAZ comments:

I think, answer should be something like this but this code gives the error below regardless of its duplicated or not:

A post with this title already exists.
Warning: Cannot modify header information - headers already sent by (output started at /home/xxx/public_html/yyy/wp-content/themes/zzz/functions.php:46) in /home/xxx/public_html/yyy/wp-includes/pluggable.php on line 897


* i have replaced my real attributes with xxx, yyy and zzz. You can still get the message.

Did you try this on your own? Is it related with my theme? (it is a woo theme: Skeptical)

AdamGold comments:

Yes, It is because I echo the error message. Please try the following (I'm not sure it will work, if you are ok with that please give me your FTP details and I will sort this out)

function check_post_uniqueness($id)

{

global $wpdb;



$post_title = $wpdb->get_var( $wpdb->prepare("SELECT post_title FROM {$wpdb->posts} WHERE ID = '{$id}' LIMIT 1") );



$wpdb->query("SELECT ID FROM {$wpdb->posts} WHERE post_title = '{$post_title}' LIMIT 1");



if ( $wpdb->num_rows > 0 ) {

return 'A post with this title already exists.';

}

return $id;

}



add_action('publish_post', 'check_post_uniqueness', 8);




AdamGold comments:

Sorry, forgot to add a line of code:

function check_post_uniqueness($id) {
global $wpdb;

$post_title = $wpdb->get_var( $wpdb->prepare("SELECT post_title FROM {$wpdb->posts} WHERE ID = '{$id}' LIMIT 1") );

$wpdb->query("SELECT ID FROM {$wpdb->posts} WHERE post_title = '{$post_title}' LIMIT 1");

if ( $wpdb->num_rows > 0 ) {
return 'A post with this title already exists.';
}
return $id;
}

add_action('publish_post', 'check_post_uniqueness', 8);
add_action('edit_post', 'check_post_uniqueness', 8);

Onur YILMAZ comments:

This time it doesn't have an effect.

You can tell me where to place or which file to change. (I have a sort of understanding, not that bad :)

AdamGold comments:

Okay. Try the first code, and put ob_start(); right after your <?php tag in functions.php, like this:

<?php
ob_start();


BTW, are you sure line 46 in functions.php is:

echo 'A post with this title already exists.';


Onur YILMAZ comments:

When i added ob_start() now it doesnt give error message but it doesn't have an effect either. It still lets to create title-2 or title-3 etc.

And i am sure line 46 includes that echo message.

AdamGold comments:

Did you use this code with ob_start(); ?
function check_post_uniqueness($id)
{
global $wpdb;
$post_title = $wpdb->get_var( $wpdb->prepare("SELECT post_title FROM {$wpdb->posts} WHERE ID = '{$id}' LIMIT 1") );

$wpdb->query("SELECT ID FROM {$wpdb->posts} WHERE post_title = '{$post_title}' LIMIT 1");

if ( $wpdb->num_rows > 0 ) {

echo 'A post with this title already exists.';

}
return $id;

}
add_action('publish_post', 'check_post_uniqueness', 8);

add_action('edit_post', 'check_post_uniqueness', 8);

Onur YILMAZ comments:

Sure, it was the first code you've sent and i used it

AdamGold comments:

Try this:
1. Remove ob_flush();
2. Replace the echo part:
echo 'A post with this title already exists.';
with:
return new WP_Error('invalid_post', __('A post with this title already exists.'));

Onur YILMAZ comments:

i cant find ob_flush()

Where do you think it exists?

AdamGold comments:

Sorry, ob_start();

Onur YILMAZ comments:

no effect :(

It still lets duplicates to be created..

AdamGold comments:

Okay I found an alternative solution. Go to wp-includes/post.php and find:

if ( $post_name_check || in_array( $slug, $feeds ) || apply_filters( 'wp_unique_post_slug_is_bad_attachment_slug', false, $slug ) ) {
$suffix = 2;


Replace with:
if ( $post_name_check || in_array( $slug, $feeds ) || apply_filters( 'wp_unique_post_slug_is_bad_attachment_slug', false, $slug ) ) {
return;

I know it's not the nicest solution but this is working :)

AdamGold comments:

Nope, not working yet. This just prevents adding the number to the URL. Sorry.

Onur YILMAZ comments:

yeah not working :(

AdamGold comments:

Sorry, out of ideas. I found a way to prevent duplicate titles like this:
if( str_replace("-pleasedontchangeuniqueduplicatetitle", "", $post_name) ) {
$error = new WP_Error('duplicate_post_title', __('Duplicate post title, Please change it.'));
return $error;
}

With some changes to the wp_unique_post_slug function but haven't found a way to display a message because you are redirected right after the save.

AdamGold comments:

Last try:
function check_post_uniqueness($id) {
global $wpdb;

$prefix = $wpdb->prefix;

$wpdb->query("DELETE bad_rows . * FROM ".$prefix."posts AS bad_rows INNER JOIN (
SELECT ".$prefix."posts.post_title, MIN( ".$prefix."posts.ID ) AS min_id
FROM ".$prefix."posts
GROUP BY post_title
HAVING COUNT( * ) >1
) AS good_rows ON ( good_rows.post_title = bad_rows.post_title
AND good_rows.min_id <> bad_rows.ID )");

$post_title = $wpdb->get_var( $wpdb->prepare("SELECT post_title FROM {$wpdb->posts} WHERE ID = '{$id}' LIMIT 1") );
$wpdb->query("SELECT ID FROM {$wpdb->posts} WHERE post_title = '{$post_title}' LIMIT 1");
if ( $wpdb->num_rows > 0 ) {
echo 'A post with this title already exists';
return 0;
}

return $id;
}

add_action('publish_post', 'check_post_uniqueness');
add_action('edit_post', 'check_post_uniqueness');

Onur YILMAZ comments:

headers already sent error :(

AdamGold comments:

I know, but this is the only way to achieve that kind of thing. It works (avoid the error), right? The post isn't being created and the error is being showed. There's a dirty way to remove the error - Go to pluggable.php line 897 and add @ before header.
@header(

AdamGold comments:

Actually it is being created just erased right after. I can't think of another way to achieve this.

AdamGold comments:

Okay, so according to the link Peter posted, HERE IS THE FINAL SOLUTION, AND IT'S WORKING:

function check_post_uniqueness($id) {
global $wpdb;

$post_title = $wpdb->get_var( $wpdb->prepare("SELECT post_title FROM {$wpdb->posts} WHERE ID = '{$id}' LIMIT 1") );

$wpdb->query("SELECT ID FROM {$wpdb->posts} WHERE post_title = '{$post_title}' LIMIT 1");

if ( $wpdb->num_rows == 1 ) {
update_option('check_post_uniqueness_notice', 'A post with this title already exists.');
update_option('display_post_uniqueness_notice', true);
$prefix = $wpdb->prefix;

$wpdb->query("DELETE bad_rows . * FROM ".$prefix."posts AS bad_rows INNER JOIN (

SELECT ".$prefix."posts.post_title, MIN( ".$prefix."posts.ID ) AS min_id

FROM ".$prefix."posts

GROUP BY post_title

HAVING COUNT( * ) >1

) AS good_rows ON ( good_rows.post_title = bad_rows.post_title

AND good_rows.min_id <> bad_rows.ID )");
}
return $id;
}
add_action('publish_post', 'check_post_uniqueness');
add_action('edit_post', 'check_post_uniqueness');


add_action('admin_head', 'add_plugin_notice');
function add_plugin_notice() {
if( get_option('display_post_uniqueness_notice') ) {
add_action('admin_notices' , create_function( '', "echo '<div class=\'updated below-h2\' id=\'message\'>" . get_option('check_post_uniqueness_notice') . "</div>';" ) );
update_option('display_post_uniqueness_notice', false);
}
}

If you can, please raise you prize because I worked kinda hard on this one :)

Onur YILMAZ comments:

Thank you for contributing everyone,

I thought this would be an easy one, but seems not :(

Adam tried hard! Even though, we couldn't have a succesful result, i think he deserved the price (he was very close though)

Regards,