php5.5新数组函数array_column

PHP5.5发布了，其中增加了一个新的数组函数array_column，感觉不错的！但是低版本PHP要使用，得自己实现：
参考地址：https://wiki.php.net/rfc/array_column

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if(!function_exists('array_column')){ function array_column($input, $columnKey, $indexKey=null){ $columnKeyIsNumber = (is_numeric($columnKey)) ? true : false; $indexKeyIsNull = (is_null($indexKey)) ? true : false; $indexKeyIsNumber = (is_numeric($indexKey)) ? true : false; $result = array(); foreach((array)$input as $key=>$row){ if($columnKeyIsNumber){ $tmp = array_slice($row, $columnKey, 1); $tmp = (is_array($tmp) && !empty($tmp)) ? current($tmp) : null; }else{ $tmp = isset($row[$columnKey]) ? $row[$columnKey] : null; } if(!$indexKeyIsNull){ if($indexKeyIsNumber){ $key = array_slice($row, $indexKey, 1); $key = (is_array($key) && !empty($key)) ? current($key) : null; $key = is_null($key) ? 0 : $key; }else{ $key = isset($row[$indexKey]) ? $row[$indexKey] : 0; } } $result[$key] = $tmp; } return $result; } } // 使用例子 $records = array( array( 'id' => 2135, 'first_name' => 'John', 'last_name' => 'Doe' ), array( 'id' => 3245, 'first_name' => 'Sally', 'last_name' => 'Smith' ), array( 'id' => 5342, 'first_name' => 'Jane', 'last_name' => 'Jones' ), array( 'id' => 5623, 'first_name' => 'Peter', 'last_name' => 'Doe' ) ); $firstNames = array_column($records, 'first_name'); print_r($firstNames); /* Array ( [0] => John [1] => Sally [2] => Jane [3] => Peter ) */ $records = array( array(1, 'John', 'Doe'), array(2, 'Sally', 'Smith'), array(3, 'Jane', 'Jones') ); $lastNames = array_column($records, 2); print_r($lastNames); /* Array ( [0] => Doe [1] => Smith [2] => Jones ) */ $mismatchedColumns = array( array( 'a' => 'foo', 'b' => 'bar', 'e' => 'baz' ), array( 'a' => 'qux', 'c' => 'quux', 'd' => 'corge' ), array( 'a' => 'grault', 'b' => 'garply', 'e' => 'waldo' ), ); $foo = array_column($mismatchedColumns, 'a', 'b'); print_r($foo); /* Array ( [bar] => foo [0] => qux [garply] => grault ) */