Added postcode validation

Example.php

@@ -1,12 +1,21 @@
 <?php
 require_once 'vendor/autoload.php';
+use \RapidWeb\Postcodes\Utils\Validator;
 use \RapidWeb\Postcodes\Factories\IdealPostcodesFactory;
 
-// You should specify IDEAL_POSTCODES_API_KEY in your .env file,
-// or pass it via the getByAPIKey method.
+$postcode = 'ST163DP';
 
-$idealPostcodes = IdealPostcodesFactory::getByEnvironment();
+$validated = Validator::validatePostcode($postcode);
 
-$addresses = $idealPostcodes->getAddressesByPostcode('ST163DP');
+if ($validated) {
 
-var_dump($addresses);
+    // You should specify IDEAL_POSTCODES_API_KEY in your .env file,
+    // or pass it via the getByAPIKey method.
+
+    $idealPostcodes = IdealPostcodesFactory::getByEnvironment();
+
+    $addresses = $idealPostcodes->getAddressesByPostcode('ST163DP');
+
+    var_dump($addresses);
+
+}

README.md

@@ -47,4 +47,15 @@ You will receive an array of addresses, appropriately split by their address lin
 
 ```php
 $addresses = $idealPostcodes->getAddressesByPostcode('ST163DP');
-```
+```
+
+### Validate postcode
+
+You can validate a UK postcode is correct using the `Validator` utility class. An example of 
+how to do so is shown below.
+
+```php
+$validated = \RapidWeb\Postcodes\Utils\Validator::::validatePostcode('ST163DP');
+```
+
+Please note that the postcode validation is case insensitive.

src/Utils/Validator.php

@@ -0,0 +1,16 @@
+<?php
+namespace RapidWeb\Postcodes\Utils;
+
+abstract class Validator
+{
+    public static function validatePostcode($postcode)
+    {
+        $postcode = strtoupper($postcode);
+
+        $regex = '#^(GIR ?0AA|[A-PR-UWYZ]([0-9]{1,2}|([A-HK-Y][0-9]([0-9ABEHMNPRV-Y])?)|[0-9][A-HJKPS-UW]) ?[0-9][ABD-HJLNP-UW-Z]{2})$#';
+
+        $result = preg_match($regex, $postcode);
+
+        return $result ? true : false;
+    }
+}