ISTWCMS-5804: adding function to uw service to check for valid external url

src/Service/UWService.php

@@ -594,4 +594,20 @@ class UWService implements UWServiceInterface {
     return $list;
   }
 
+  /**
+   * {@inheritDoc}
+   */
+  public function validExternalUrl(string $url): bool {
+
+    // Get the headers of the URL.
+    $headers = @get_headers($url);
+
+    // Use condition to check if there is no URL.
+    if($headers && strpos( $headers[0], '404')) {
+      return FALSE;
+    }
+
+    return TRUE;
+  }
+
 }

src/Service/UWServiceInterface.php

@@ -211,4 +211,14 @@ interface UWServiceInterface {
    */
   public function getContentTypeUsage(array $content_types, bool $show_null_content_types): array;
 
+  /**
+   * Function to check if an external url is valid.
+   *
+   * @param string $url
+   *   The URL to be checked.
+   *
+   * @return bool
+   *   Whether url is valid or not.
+   */
+  public function validExternalUrl(string $url): bool;
 }