Some options in terms of making code self-documenting

gistfile1.php

<?php
// SHORTEST VERSION
if ( in_array( $_SERVER[ 'REMOTE_ADDR' ], array( '127.0.0.1', ) ) ) {
  toughp_backup_site( $_GET[ 'home_url' ], $_GET[ 'key' ] );
}







// LONGEST VERSION

// Performing a backup is initiated through an http request
// We can not allow access to this action to arbitrary IP addresses
// So we whitelist IP addresses allowed to perform backups
$ip_addresses_allowed_to_initiate_backup = array( '127.0.0.1', );
$ip_address_trying_to_initiate_backup = $_SERVER[ 'REMOTE_ADDR' ];

$backup_is_being_initiated_by_an_allowed_ip_address = in_array( $ip_address_trying_to_initiate_backup, $ip_addresses_allowed_to_initiate_backup );

if ( $backup_is_being_initiated_by_an_allowed_ip_address ) { 
  $home_url = $_GET[ 'home_url' ];
  $key = $_GET[ 'key' ];
  toughp_backup_site( $home_url, $key );
}