note 75351 deleted from function.is-array by danbrown

Note Submitter: elanthis at awesomeplay dot com ---- First, "sequential array" is a silly term. Use "vector." Likewise, it's not an "associative array," it's a "map." We have common computer science terms for a reason. :) "If the keys were all numbers then we'd call it "sequential"." But that's not true. The following array, with all-numeric keys, is a map, not a vector: $ar[1] = 'foo'; $ar[12] = 'bar'; $ar[578] = 'baz'; A vector would be an array in which all keys are integers, each successive key is equal to the previous key plus one, and the first key is 0. So, the only proper, always correct, fail-proof way I can think of to do this is (and this is lame we have to do ths, since the internal PHP implementation clearly knows in a much more efficient manner): function is_vector (&$array) { $next = 0; foreach ($array as $k=>$v) { if ($k != $next) return false; $next++; } return true; } Yes, it might look cleaner to use array_keys() in there, but I think that will be far more inefficient, since it would have to create a whole new array and copy all the keys into it. The above should be faster. In theory.