WP: Add fields to user profile

contact_method.php

<?php
function modify_contact_methods($profile_fields) {

	// Add new fields
	$profile_fields['twitter'] = 'Twitter Username';
	$profile_fields['facebook'] = 'Facebook URL';
	$profile_fields['gplus'] = 'Google+ URL';

	// Remove old fields
	unset($profile_fields['aim']);

	return $profile_fields;
}
add_filter('user_contactmethods', 'modify_contact_methods');

user_profile.php

<?php
add_action( 'personal_options_update', 'save_custom_profile_fields' );
add_action( 'edit_user_profile_update', 'save_custom_profile_fields' );
function save_custom_profile_fields( $user_id ) {
   update_user_meta( $user_id, 'phone_number', $_POST['phone_number'], get_user_meta( $user_id, 'phone_number', true ) );
   update_user_meta( $user_id, 'greeting', $_POST['greeting'], get_user_meta( $user_id, 'greeting', true ) );
}

add_filter( 'user_contactmethods', 'add_contact_option', 10, 2 );
function add_contact_option( $user_contactmethods, $user ) {
   $user_contactmethods['phone_number'] = 'Phone Number';
   return $user_contactmethods;
}

add_action( 'personal_options', 'add_profile_options');
function add_profile_options( $profileuser ) {
   $greeting = get_user_meta($profileuser->ID, 'greeting', true);
   ?><tr>
   <th scope="row">Greeting</th>
   <td><input type="text" name="greeting" value="<?php echo $greeting; ?>" /></td>
   </tr><?php
}