Please let me know if I am in a right direction with fixing rel="canonical" issue?

[kirupa]

While doing my website crawl, I keep getting the message that I have tons of duplicated pages.
http://example.com/index.php and http://www.example.com/index.php are considered to be the duplicates. As I figured out this one: http://example.com/index.php is a canonical page, and I should point out this one: http://www.example.com/index.php to it. Could you please let me know if I will do a right thing if I put this piece of code into my index.php file?
? Or I should use this one:

[LoganRay]

Hi,

Ideally, you would handle www and nonwww duplication by way of a redirect rule. Both versions of that URL should not render, i.e. when you go to www.example.com it should take you straight over to example.com.

You can handle this with canonical tags the way you've proposed, the URL in the href element should be the one you prefer. However, this should be reserved only as a work-around in the event that you can't get implement a server-side redirect rule to handle ALL www-to-nonwww issues.

[MikeRoberts]

As Logan said, you'd be better served handling these with 301 redirects. But you will also want to go in Google Search Console/Webmaster tools into Site Settings and set your preferred domain to either WWW on Non-WWW (depending on which you prefer to show across your site).

[kirupa]

Thanks for your reply, Logan. Why exactly 301 redirect is better than handling this with canonical tags? Canonical tags wouldn't take so much time, would they?

[kirupa]

Thank you, will do!

[LoganRay]

This type of duplicate applies to far more than just the homepage...so by implementing a single redirect rule, you handle this type of duplicate for every single URL on your site, and neither people nor search engines will ever see the undesired version.

If you do this via canonical tags, you have to include the canonical tag on every page, which could be very time consuming depending on how large your site is.