Temporary solution for adding a Custom column button to WordPress 3.4.2 becomes invalid

Many children's shoes found that after they upgraded to WordPress 3.4.2, the buttons for adding custom columns failed. This may be the most obvious BUG in all versions of WP. The results of crazy upgrades ....
 
Although the official team has not responded to this BUG, some unofficial fixes have been provided. You do not have to wait for the version upgrade. Use this plug-in to temporarily solve the problem.
 
Plug-in: http://wordpress.org/extend/plugins/hotfix/
 
Upload the space plug-in directory and enable it.
 
Or Add the following code to the topic's functions template.
 
<? Php
/*
Plugin Name: Fix Custom Fields in WP 3.4.2
Version: 0.1
Plugin URI: http://core.trac.wordpress.org/ticket/21829
Description: Implements a workaround for adding and updating custom fields in WordPress 3.4.2.
Author: Sergey Biryukov
Author URI: http://profiles.wordpress.org/sergeybiryukov/
*/
 
Function fix_custom_fields_in_wp342 (){
Global $ wp_version, $ hook_suffix;
 
If ('3. 4.2 '===$ wp_version & in_array ($ hook_suffix, array ('Post. php', 'post-new. php'):?>
<Script type = "text/javascript">
JQuery (document). delegate ('# addmetasub, # updatemeta', 'hover focal ', function (){
JQuery (this). attr ('id', 'meta-add-submit ');
});
</Script>
<? Php
Endif;
}
Add_action ('admin _ print_footer_scripts ', 'fix _ custom_fields_in_wp342 ');
?>
Source: http://core.trac.wordpress.org/attachment/ticket/21829/fix-custom-fields-in-wp342.php
 
I believe the official website will soon fix this BUG.