Disable the WordPress core upgrade function for your clients

Ever had a client call you up and say “Hey there is this message on the WordPress dashboard saying that I need to upgrade, what should I do?” no? well I have on many occasions. Here is a simple trick to stop it from showing up in the admin dashboard area so as to eliminate the confusion for your clients. Remember tho that it is always a good idea to keep your WordPress installations up-to-date for security purposes. I am sure that being the Admin of your clients sites you will be keeping an eye on new version releases and kindly login and upgrade their installs for them like I do.

Simply copy this code on your functions.php

add_action( 'init', create_function( '$a', "remove_action( 'init', 'wp_version_check' );" ), 2 );
add_filter( 'pre_option_update_core', create_function( '$a', "return null;" ) );

# 2.8 to 3.0:
remove_action( 'wp_version_check', 'wp_version_check' );
remove_action( 'admin_init', '_maybe_update_core' );
add_filter( 'pre_transient_update_core', create_function( '$a', "return null;" ) );

# 3.0:
add_filter( 'pre_site_transient_update_core', create_function( '$a', "return null;" ) );