note 107690 added to function.array-map

Hope I'm not late to the party, here's my function to apply array_map to the *keys* of an array. Extra array arguments will be used for the callback function's parameters just like with array_map, with the difference that a string is also allowed: it will just be used to create an array of appropriate length with as each value that string. Arrays are left alone (and will be padded with nulls by array_map as needed). <?php //_________________________________________________ // array_map_keys($callback, $array, [$args, ..]) / function array_map_keys($callback, $array /* [, $args ..] */) { $args = func_get_args(); if (! is_callable($callback)) trigger_error("first argument (callback) is not a valid function", E_USER_ERROR); if (! is_array($array)) trigger_error("second argument must be an array", E_USER_ERROR); $args[1] = array_keys($array); // If any additional arguments are not arrays, assume that value is wanted for every $array item. // array_map() will pad shorter arrays with Null values for ($i=2; $i < count($args); $i++) { if (! is_array($args[$i])) { $args[$i] = array_fill(0, count($array), $args[$i]); } } return array_combine(call_user_func_array('array_map', $args), $array); } // Some examples: $arr = array('foo'=>123, 'bar'=>456); // simply uppercase keys: var_dump(array_map_keys('strtoupper', $arr)); // or.. var_dump(array_map_keys(function($input) {return strtoupper($input);}, $arr)); // >> array(2) { ["FOO"]=>int(123) , ["BAR"]=> int(456) } // Add a prefix 'myvar_': var_dump(array_map_keys(function($input, $prefix) {return $prefix.$input;}, $arr, 'myvar_')); // >> array(2) { ["myvar_foo"]=>int(123) , ["myvar_bar"]=>int(456) } // Apart from the (static string) prefix, we also number them: $arr = array('foo'=>123, 'bar'=>456, 'bazz'=>789, 'yadda'=>'0AB'); var_dump(array_map_keys(function($input, $middle, $number) {return $number.':'.$middle.$input;}, $arr, 'myvar_', range(1, count($arr)))); // >> array(4) { ["1:myvar_foo"]=>int(123) , ["2:myvar_bar"]=>int(456) , ["3:myvar_bazz"]=>int(789) , ["4:myvar_yadda"]=>string(3) "0AB" } ?> ---- Server IP: 83.137.20.135 Probable Submitter: 82.73.20.238 ---- Manual Page -- http://www.php.net/manual/en/function.array-map.php Edit -- https://master.php.net/note/edit/107690 Del: integrated -- https://master.php.net/note/delete/107690/integrated Del: useless -- https://master.php.net/note/delete/107690/useless Del: bad code -- https://master.php.net/note/delete/107690/bad+code Del: spam -- https://master.php.net/note/delete/107690/spam Del: non-english -- https://master.php.net/note/delete/107690/non-english Del: in docs -- https://master.php.net/note/delete/107690/in+docs Del: other reasons-- https://master.php.net/note/delete/107690 Reject -- https://master.php.net/note/reject/107690 Search -- https://master.php.net/manage/user-notes.php