Description:
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Currently, in PHP, if you want to reference the last character of a string, you'd need to do something like $x{strlen($x)-1}.  If using substr, however, you can do substr($x,-1,1) or substr($x,strlen($x)-1,1).  In keeping with the former substr example, $x{-1} could be made to access the last character of a string as well.  Since, right now, using negative numbers will result in a warning, it seems unlikely that any existing code is going to be broken by such a change...