It's quite convenient and easy to use Google to store your contacts, especially when you are using more than one of the services Google provided. If you're intended to have all your Gmail contacts on your iPhone, then this article is the one that you need right now. You'll find tutorials on how to sync Google contacts on iPhone with CardDAV.
CardDAV is an address book client/server protocol designed to allow users to access and share contact data on a server. It's built around HTTP-based WebDAV protocol and uses vCard format for contact data. The open protocol is announced in August 2011.
Using CardDAV to sync your iOS Contacts means that "you'll be able to edit, add, and remove contacts from your device and keep them in sync everywhere you use them".
To download this tool, you can go to Google Play.
As long as you have downloaded CardDAV to your PC, you can then follow the steps below to sync iPhone contacts with Google.
When the setup is completed, open the Phone or Contacts app, your Google contacts will appear in the list. This group is now in sync with Google and will update when contacts are added or changed on either end.
Possibly you may lose contacts on iPhone because you press the wrong button, fail to jailbreak iPhone, etc. In such cases you can rescue all iPhone contacts by using Tenorshare iPhone Data Recovery, an user friendly tool that helps you recover contacts, photos, text messages and other files from your iPhone 5, iPhone 4S, iPhone 4 and more.