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URL inclusion as absolute links
Indeed, an include with http:// generates an apache hit (PHP opens a connection on port 80 for the entered address — and, in doing so, also makes a resolve DNS request - requests the page, then integrates it in the current code) for each include of each file.
As such, a well structured and optimised website will find itself totally saturating the web server as a result of this process. An include file /site/web/* only performs a local fopen on PHP, no DNS, no Apache.
Please also refer to this FAQ (click here) about this topic.
Link to this FAQ: