Admin attempt to create user using an existing email yields PHP notice

[coffee2code]

When the admin interface is used to create a new user, a PHP notice is generated due to an attempt to access an undefined property of an object.

In edit_user() in wp-admin/includes/user.php, there exists this check for uniqueness of the user email:

elseif ( ( $owner_id = email_exists($user->user_email) ) && $owner_id != $user->ID ) {

When a new user is created, this function is also used but the $user object is not assigned an ID variable. So when the email_exists() check is true, the second half of the conditional generates a PHP notice because $user->ID is not defined. Specifically, here's the output with WP_DEBUG set to true:

Notice: Undefined property: stdClass::$ID in /Users/scott/Sites/wp30.dev/wp-admin/includes/user.php on line 172

In order to see this transitional message and to verify the contents of $user, I hooked the 'user_profile_update_errors' action:

add_action ( 'user_profile_update_errors', 'var_dump_user', 1, 3 );
function var_dump_user( $errors, $update, $user ) {
	var_dump( $user );
	exit();
}

Which yields:

object(stdClass)#105 (9) { ["user_login"]=> string(8) "testuser" ["role"]=> string(10) "subscriber" ["user_email"]=> string(16) "xxxxxx@gmail.com" ["user_url"]=> string(0) "" ["first_name"]=> string(0) "" ["last_name"]=> string(0) "" ["comment_shortcuts"]=> string(0) "" ["use_ssl"]=> int(0) ["user_pass"]=> string(6) "mypass" }

(Note no 'ID' is defined.)

My proposed fix (in the first attached diff) is to change the elseif conditional to be:

elseif ( ( $owner_id = email_exists($user->user_email) ) && ( !$update || ( $owner_id != $user->ID ) ) ) {

In this case, if the email exists and either a user is being created (!$update) or a user is being updated but is not the account associated with the email ( $owner_id != $user->ID ), then the WP error we want gets generated, while no PHP notices get generated.

FYI: The code in user.php was introduced in [10990] in response to #9563.

[ryan]

(In [15799]) Fix notice when creating users. Props coffee2code. fixes #14286