PHPの2次元配列値関数array_columnの使用に対応

if(!function_exists('array_column')){ <br />    function array_column($input, $columnKey, $indexKey=null){ <br />        $columnKeyIsNumber      = (is_numeric($columnKey)) ? true : false; <br />        $indexKeyIsNull         = (is_null($indexKey)) ? true : false; <br />        $indexKeyIsNumber       = (is_numeric($indexKey)) ? true : false; <br />        $result                 = array(); <br />        foreach((array)$input as $key=>$row){ <br />            if($columnKeyIsNumber){ <br />                $tmp            = array_slice($row, $columnKey, 1); <br />                $tmp            = (is_array($tmp) && !empty($tmp)) ? current($tmp) : null; <br />            }else{ <br />                $tmp            = isset($row[$columnKey]) ? $row[$columnKey] : null; <br />            } <br />            if(!$indexKeyIsNull){ <br />                if($indexKeyIsNumber){ <br />                    $key        = array_slice($row, $indexKey, 1); <br />                    $key        = (is_array($key) && !empty($key)) ? current($key) : null; <br />                    $key        = is_null($key) ? 0 : $key; <br />                }else{ <br />                    $key        = isset($row[$indexKey]) ? $row[$indexKey] : 0; <br />                } <br />            } <br />            $result[$key]       = $tmp; <br />        } <br />        return $result; <br />    } <br />} 

$records = array( <br />    array( <br />        'id' => 2135, <br />        'first_name' => 'John', <br />        'last_name' => 'Doe'<br />    ), <br />    array( <br />        'id' => 3245, <br />        'first_name' => 'Sally', <br />        'last_name' => 'Smith'<br />    ), <br />    array( <br />        'id' => 5342, <br />        'first_name' => 'Jane', <br />        'last_name' => 'Jones'<br />    ), <br />    array( <br />        'id' => 5623, <br />        'first_name' => 'Peter', <br />        'last_name' => 'Doe'<br />    ) <br />); <br />$firstNames = array_column($records, 'first_name'); <br />print_r($firstNames);