This it not an issue with your browser, but instead an issue with the PHP header function being immune to HTTP splitting attacks. The same goes for set-cookie function call.

You can read more about this here http://stackoverflow.com/questions/6287713/is-php-immune-to-http-response-splitting-vulnerabilities

A short excerpt:

 [...] Although response splitting is not specific to PHP, the PHP interpreter 
contains protection against the attack since version 4.4.2 and 5.1.2. [1]

This it not an issue with your browser, but instead an issue with the PHP header function being immune to HTTP splitting attacks. The same goes for set-cookie function call.

You can read more about this here https://stackoverflow.com/questions/6287713/is-php-immune-to-http-response-splitting-vulnerabilities

A short excerpt:

 [...] Although response splitting is not specific to PHP, the PHP interpreter 
contains protection against the attack since version 4.4.2 and 5.1.2. [1]