Get array of avaiable ip's fitered by criteria (eg. exclude local interfaces)

class-get-available-ip-adresses.php

/**
* Rested on centos 5, 6, 7 
* Requires yum install net-tools on centos 7 
*/
class GetAvailableIpAdresses {
	/**
	 * @var $excludeIp array of IP's to exclude in IPV4 format eg. 127.0.0.1
	 */
	private static $excludeIp;	
	/**
	 * Filter array
	 * @param  array $excludeIp    array of IP's to exclude in IPV4 format eg. 127.0.0.1
	 * @return array filtered array of avaiable ip's
	 */
	public static function get( $excludeIp = array( '127.0.0.1', '10.0.0.0/8', '192.168.0.0/16') ) {
		self::$excludeIp = $excludeIp;

		return array_filter( self::get_avaiable_ip_addresses(), array(get_class(), 'ip_range_filter'));
	}
	/**
	 * Get array of all avaiable ip's 
	 * @return array of avaiable ip's
	 */	
	private static function get_avaiable_ip_addresses() {
		$nl = '\n';
		$cmd = <<<EOT
ifconfig | grep "inet " | awk 'begin{FS="$nl";RS="$nl$nl"}{gsub(/addr:/, "");split($0,a," ");print a[2];}'		
EOT;

		return explode( PHP_EOL, trim(shell_exec($cmd)) );
	}
	/**
	 * Filter array 
	 * @param  string $ip    IP to check in IPV4 format eg. 127.0.0.1 
	 * @return boolean true if the ip is in this range / false if not.
	 */
	private static function ip_range_filter( $ip ) {
		foreach ( self::$excludeIp as $range) {
			if ( self::ip_range_check($ip, $range)) {
				return false;
			}
		}
		
		return true;
	}
	/**
	 * Check if a given ip is in a network
	 * @param  string $ip    IP to check in IPV4 format eg. 127.0.0.1
	 * @param  string $range IP/CIDR netmask eg. 127.0.0.0/24, also 127.0.0.1 is accepted and /32 assumed
	 * @return boolean true if the ip is in this range / false if not.
	 */
	private static function ip_range_check( $ip, $range ) {
		if ( strpos( $range, '/' ) == false ) {
			$range .= '/32';
		}
		// $range is in IP/CIDR format eg 127.0.0.1/24
		list( $range, $netmask ) = explode( '/', $range, 2 );
		$range_decimal = ip2long( $range );
		$ip_decimal = ip2long( $ip );
		$wildcard_decimal = pow( 2, ( 32 - $netmask ) ) - 1;
		$netmask_decimal = ~ $wildcard_decimal;
		return ( ( $ip_decimal & $netmask_decimal ) == ( $range_decimal & $netmask_decimal ) );
	}
}