Add meta tags to a custom header

Question

I'm trying to create php code to change the Wordpress header. With the help of https://wordpress.stackexchange.com/a/134524, I have the following:

add_filter( 'wp_headers', 'add_meta_to_header' );
function add_meta_to_header($headers) { 
    if ( is_page('Page title') ) {
        $headers['X-UA-Compatible'] = 'IE=edge,chrome=1';
    }
    return $headers;
}

My problem is I don't know what the syntax should be to add multiple meta tags to the header. For example I would like to add: <meta name='twitter:card' content='summary_large_image'/>. How should I include this inside the if statement?

Should that then be something like: headers['meta name, content'] = 'twitter:card, summary_large_image';?

Answer 1

HTTP headers are different than the HTML head. The meta tag you're looking to add (for the Twitter card) is actually a meta tag that gets place in the HTML head.

So to achieve exactly what you're looking to do from a PHP "functions" file, you'd want to hook into wp_head instead. Like this:

add_action('wp_head', function(){
    echo '<meta name="twitter:card" content="summary_large_image" />';
});

You can piggyback on a single hook to add as many meta tags as you need (since I see you're declaring the large summary size for Twitter, you'll probably want to tell it which image to use as well. You can do it like this:

add_action('wp_head', function(){
    echo '<meta name="twitter:card" content="summary_large_image" />';
    echo '<meta name="twitter:image" content="' . get_the_post_thumbnail_url() . '" />'; //The post thumbnail is the featured image– you could change this to a different image if desired
    echo '<meta name="twitter:creator" content="@yourtwitterusername" />'; //You can add the Twitter username of the author here (by hardcoding or even pull from the author's profile)
});

Think of the WordPress actions (or "hooks") as points when things happen– so the above code just tells WordPress: "hey, when you trigger the wp_head action, run this code as well".

Here is a list of all (or most) of the WP actions. I use this list all the time, so it's worth a bookmark.

Remember with filters you need to return, but with actions you just do what you want to happen at that point (which is why we are just echoing here).

Sidenote: I know the is_page() function accepts strings, but using the page title here can be fragile in case the title ever gets changed. Consider using the post ID there instead– so like is_page(123)

Hope that helps!