I typically refer to any assets on my site using absolute path so that I don\'t have to worry about the location of the assets relative to current file.
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I hate to say this but none of the above provides the solution. The answers by @Zoltan and @stslavik were close but, unfortunately, didn't work when deployed; I wished one of them worked, though.
As a result, I resorted to using a combination of named constants and include files in PHP. More details: File Structure for a PHP Project. Note that it doesn't have to be PHP; you can use other languages that provide similar features. +1 for @margusholland whose answer led me to experiment with this solution.