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Background: Trevor is working with a PHP implementation of a standard algorithm: take a main set of default name-value pairs, and update those name-value pairs, but only for those name-value pairs where a valid update value actually exists. Problem: by default, PHP array_merge works like this ... it will overwrite a non-blank value with a blank value. $aamain = Array('firstname'=>'peter','age'=>'32','nation'=>''); $update = Array('firstname' => '','lastname' => 'griffin', age =>'33','nation'=>'usa'); print_r(array_merge($aamain,$update)); /* Array ( [firstname] => // <-- update set this to blank, NOT COOL! [age] => 33 // <-- update set this to 33, thats cool [lastname] => griffin // <-- update added this key-value pair, thats cool [nation] => usa // <-- update filled in a blank, thats cool. ) */ Question: What's the fewest-lines-of-code way to do array_merge where blank values never overwrite already-existing values? print_r(array_coolmerge($aamain,$update)); /* Array ( [firstname] => peter // <-- don't blank out a value if one already exists! [age] => 33 [lastname] => griffin [nation] => usa ) */ UPDATE: 2016-06-17T11:51:54 the question was updated with clarifying context and rename of variables.

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