X-UA-Compatibility with HTTP Header

[mjabado]

actually i'm having a problem with a website in IE which is not on intranet and the "always show pages in compatibility mode is not activated" but it still opens in quirks mode sometimes, despite adding

<meta http-equiv="X-UA-Compatible" content="IE=edge"/>

I have red that i can send this compatibility order in an HTTP Header or in htaccess

My problem is that i have searched on how to send an HTTP header and actually found no clue, and btw i'm a php developer just in case this information was necessary.

I would really appreciate if someone could provide me what's needed to add (for both, or for one at least) and how/where to add it, i have been looking for the whole week and it's quiet urgent to find the fix so soon !

Is this way to send it as an HTTP header as a first line in the page is right ?

<?php
header('X-UA-Compatible: IE=edge');
?>

I really appreciate any help can be provided and i'm thankful in advance

[Fou-Lu]

That's correct.
So long as its called before any output has occurred, than it will add the header to the headers stack to send.
Now if the browser accepts it is an entirely different thing. It is an extension setting, so there would be no way to force that.