How to create a mobile, hackable, wp-config.php file for local, staging, and production environments (how I do it anyway).

wp-config.php

<?php

/**
 * The base configurations of the WordPress.
 *
 * This file has the following configurations: MySQL settings, Table Prefix,
 * Secret Keys, WordPress Language, and ABSPATH. You can find more information
 * by visiting {@link http://codex.wordpress.org/Editing_wp-config.php Editing
 * wp-config.php} Codex page. You can get the MySQL settings from your web host.
 *
 * This file is used by the wp-config.php creation script during the
 * installation. You don't have to use the web site, you can just copy this file
 * to "wp-config.php" and fill in the values.
 *
 * @package WordPress
 */

// Production
if(
	$_SERVER['HTTP_HOST'] == 'example.com'
		 
  	// Make sure and include circa 1994
	|| $_SERVER['HTTP_HOST'] == 'www.example.com'
) {

	// ** MySQL settings - You can get this info from your web host ** //
	/** The name of the database for WordPress */
	define('DB_NAME', 'example.com');

	/** MySQL database username */
	define('DB_USER', 'user');

	/** MySQL database password */
	define('DB_PASSWORD', 'password');

	/** MySQL hostname */
	define('DB_HOST', 'localhost');

	/** Database Charset to use in creating database tables. */
	define('DB_CHARSET', 'utf8');

	/** The Database Collate type. Don't change this if in doubt. */
	define('DB_COLLATE', '');

	/**
	 * For developers: WordPress debugging mode.
	 *
	 * Change this to true to enable the display of notices during development.
	 * It is strongly recommended that plugin and theme developers use WP_DEBUG
	 * in their development environments.
	 */
	define('WP_DEBUG', false);

	// Just in case we copied this over, let's clear it out.
	if( file_exists( 'robots.txt' ) ){
		file_put_contents( 'robots.txt', "" );
	}


}

// Staging
if( $_SERVER['HTTP_HOST'] == 'example.stagingdomain.com' ) {

	// ** MySQL settings - You can get this info from your web host ** //
	/** The name of the database for WordPress */
	define('DB_NAME', 'example.stagingdomain.com');

	/** MySQL database username */
	define('DB_USER', 'user');

	/** MySQL database password */
	define('DB_PASSWORD', 'password');

	/** MySQL hostname */
	define('DB_HOST', 'localhost');

	/** Database Charset to use in creating database tables. */
	define('DB_CHARSET', 'utf8');

	/** The Database Collate type. Don't change this if in doubt. */
	define('DB_COLLATE', '');

	/**
	* For developers: WordPress debugging mode.
	*
	* Change this to true to enable the display of notices during development.
	* It is strongly recommended that plugin and theme developers use WP_DEBUG
	* in their development environments.
	*/
	define('WP_DEBUG', true); // Yes, let's even smash notices on staging.
	
  	// Keeps the Googlers away...
	if( ! file_exists( 'robots.txt' ) ){
		file_put_contents( 'robots.txt', "User-agent: *\nDisallow: /" );
	}

}

// @aubreypwd's VVV Development
if( $_SERVER['HTTP_HOST'] == 'example.com.dev' ) {

	// ** MySQL settings - You can get this info from your web host ** //
	/** The name of the database for WordPress */
	define('DB_NAME', 'example.com.dev');

	/** MySQL database username */
	define('DB_USER', 'root');

	/** MySQL database password */
	define('DB_PASSWORD', 'root');

	/** MySQL hostname */
	define('DB_HOST', 'localhost');

	/** Database Charset to use in creating database tables. */
	define('DB_CHARSET', 'utf8');

	/** The Database Collate type. Don't change this if in doubt. */
	define('DB_COLLATE', '');

	/**
	 * For developers: WordPress debugging mode.
	 *
	 * Change this to true to enable the display of notices during development.
	 * It is strongly recommended that plugin and theme developers use WP_DEBUG
	 * in their development environments.
	 */
	define('WP_DEBUG', true);
	
	// Just in case we copied this over, let's clear it out.
	if( file_exists( 'robots.txt' ) ){
		file_put_contents( 'robots.txt', "" );
	}
	
}

/* No matter where you move your site to, the domains, URL's, etc will follow whatever domain it's on. */
define( 'WP_HOME', 		'http://' . $_SERVER['HTTP_HOST'] );
define( 'WP_SITEURL', 		'http://' . $_SERVER['HTTP_HOST'] );
define( 'WP_PLUGIN_DIR', 	realpath( 	$_SERVER['DOCUMENT_ROOT'] 	. '/wp-content/plugins' ) );
define( 'WP_PLUGIN_URL', 	'http://' . $_SERVER['HTTP_HOST']  		. '/wp-content/plugins' );
define( 'WP_THEMES_DIR', 	realpath( 	$_SERVER['DOCUMENT_ROOT'] 	. '/wp-content/themes' 	) );
define( 'WP_THEMES_URL', 	'http://' . $_SERVER['HTTP_HOST']  		. '/wp-content/themes' );
define( 'WP_CONTENT_DIR', 	realpath( 	$_SERVER['DOCUMENT_ROOT'] 	. '/wp-content' ) );
define( 'WP_CONTENT_URL', 	'http://' . $_SERVER['HTTP_HOST']  		. '/wp-content' );

/**#@+
 * Authentication Unique Keys and Salts.
 *
 * Change these to different unique phrases!
 * You can generate these using the {@link https://api.wordpress.org/secret-key/1.1/salt/ WordPress.org secret-key service}
 * You can change these at any point in time to invalidate all existing cookies. This will force all users to have to log in again.
 *
 * @since 2.6.0
 */
define('AUTH_KEY',         '`&d|.pQF>n]@tOH%4zh>-]8[,ds>m>3s@|DVFR3+hf]=cv8E3=b-uq8kmD6O~-YW'); // Please change these.
define('SECURE_AUTH_KEY',  '|IN0`k(4t<|Ah/Vs|_4$+{@MfM>j0v#oO%-Av02cKG;+nznO&$&{+iX`2Q]8pl|0');
define('LOGGED_IN_KEY',    'IilYZndF|E|hEp+!A$v~?KBMCJFr/XK-wApq~x=H$z>wQRyX[.I]`7>cnpd4-w5P');
define('NONCE_KEY',        ':lD]$YHB/O^?)orWlsIv+6!8X9D8A|chM|0$uW/*wrOI6sdR@Z`I#VLAz!-[_tiX');
define('AUTH_SALT',        'fDuVZY5gZcw>D=@E(3%M<IPdtQCdb?DK$gjOKj$j|5)m]_DtC6pxm$M?cX|U?K:T');
define('SECURE_AUTH_SALT', 'ZTXr[ep-y*}o:c|>t9 0g^b?%[QcD%|<jp;+^,B=T(-t(#Tm]QS{.dX=$Z8)9gKF');
define('LOGGED_IN_SALT',   '~V><>Q1o!O$Bq1DsAHGcvd%kr/m(-<6(Nf`v&60rIfg3Ljxhx/sTs;&N*@qexp}g');
define('NONCE_SALT',       'A>r;S!6JcnC-DTv4t@VYSs Ag|xXExZ58LH(2)3rP;Nk79lo-rqqpcQ02W!oW|-$');

/**#@-*/

/**
 * WordPress Database Table prefix.
 *
 * You can have multiple installations in one database if you give each a unique
 * prefix. Only numbers, letters, and underscores please!
 */
$table_prefix  = 'wp_'; //Yours is different.

/**
 * WordPress Localized Language, defaults to English.
 *
 * Change this to localize WordPress. A corresponding MO file for the chosen
 * language must be installed to wp-content/languages. For example, install
 * de_DE.mo to wp-content/languages and set WPLANG to 'de_DE' to enable German
 * language support.
 */
define('WPLANG', '');

/* That's all, stop editing! Happy blogging. */

/** Absolute path to the WordPress directory. */
if ( !defined('ABSPATH') )
	define('ABSPATH', dirname(__FILE__) . '/');

/** Sets up WordPress vars and included files. */
require_once(ABSPATH . 'wp-settings.php');