When metadata or link elements are identical across most of a large website, maintenance is slower and costlier.

Suggestion: Add a file of website meta and link elements that apply to an entire website.

Exceptions should be supported. If the same meta or link element with the same attribute also appears in a page file, regardless of the value, the one appearing in the page file would get precedence.

Very large sites may need directory specificity. A file of directory-specific meta and link elements would override the website-wide file of meta and link elements, while being overridden by the same element-attribute pairs written into a specific page.

I don't program in PHP, but I suspect this being in HTML would mean faster page loading.

Example: The author of a whole website might be Chris, which need be said in only one place, the website file; except that the author of the Executive subdirectory might be Pat, which need be said in only one place, the directory file; except that the author of the one-page CEO's Letter might be Landry, which need be said in only one place, in the HTML page's head element.