WordPress: Adding custom user/profile fields manually

wp-profile-fields.php

	function my_show_extra_profile_fields( $user ) { ?>
		<div class="subscription-info">
		<h3>Subscription Information</h3>
		<table class="form-table">
			<tr>
				<th><label for="subscription">Customer ID</label></th>

				<td>
					<input type="text" name="subscription" id="subscription" value="<?php echo esc_attr( get_user_meta( $user->ID, 'subscription', 1) ); ?>" class="regular-text" /><br />
					<span class="description">Please enter your customer ID.</span>
				</td>
			</tr>

		</table>
		</div>
	<?php }


	function my_save_extra_profile_fields( $user_id ) {
		if ( !current_user_can( 'edit_user', $user_id ) )
			return false;
		/* Copy and paste this line for additional fields. Make sure to change 'subscription' to the field ID. */
		update_user_meta( $user_id, 'subscription', $_POST['subscription'] );
	}

	// custom profile fields
	add_action( 'show_user_profile', 'my_show_extra_profile_fields', 5 );
	add_action( 'edit_user_profile', 'my_show_extra_profile_fields', 5 );
	add_action( 'personal_options_update', 'my_save_extra_profile_fields' );
	add_action( 'edit_user_profile_update', 'my_save_extra_profile_fields' );