In previous versions of WordPress, when you called get_userdata() or get_user_by(), you got a plain stdClass object, filled with all the fields from both wp_users and wp_usermeta tables. This had two disadvantages:

• dashes were removed, so that ‘my-custom-field’ became ‘mycustomfield’
• all fields were loaded and kept in memory, wasting precious resources

Since WordPress 3.3, all user-related functions return WP_User instances. This class has some magic methods that make it behave as if it contained all the custom fields.

Accessing a single custom field

For example, let’s try to display the user description of the currently logged in user:

$current_user = wp_get_current_user();
 
if ( isset( $current_user->bio ) )
	echo '<p>' . $current_user->bio . '</p>';

This code works fine both in WP 3.2 and in WP 3.3. The difference is that in WP 3.3 that code is equivalent to this:

if ( $current_user->__isset( 'bio' ) ) )
	echo '<p>' . $current_user->__get( 'bio' ) . '</p>';

Internally, the __isset() and __get() methods call get_user_meta().

If you have a variable key or a key with dashes, there are prettier aliases which you can use:

if ( $current_user->has_prop( 'my-field' ) ) )
	echo '<p>' . $current_user->get( 'my-field' ) . '</p>';

Accessing all custom fields

Unfortunately, iterating over all the custom fields by casting to an array isn’t possible anymore:

foreach ( (array) $user as $key => $value ) {
	var_dump( $key, $value );
}

It will have to be replaced with this:

foreach ( get_user_meta( $user->ID ) as $key => $values ) {
	var_dump( $key, $values );
}

Note that, in the later case, $values is an array.