How To Change Default User Agent String Using PHP

The user agent string of the browser can't be changed by default. But we often see, the logs of website visitors say, user agents were "Google Bot". What is this? Is this a special website browser used by Google? No, This is the website crawler engine of Google. The server where the crawler script is hosted sends this string in the header while sending an http request for crawling your web page. So, it's quite clear that if the visitor of a web page is not a browser (ie. a human user), then the user agent string must be sent by the server software (Apache or IIS or whatever you have). Now in this short tutorial I'll show you how to change the default user agent string of your server using PHP.