php5.5新数组函数array_column使用

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：

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
)
*/

array_column 用于获取二维数组中的元素(php 5 >= 5.5.0)

<?php
// array representing a possible record set returned from a database
$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',
    )
);

$first_names = array_column($records, 'first_name');
print_r($first_names);
?>
array
(
    [0] => john
    [1] => sally
    [2] => jane
    [3] => peter
)<?php
// using the $records array from example #1
$last_names = array_column($records, 'last_name', 'id');
print_r($last_names);
?>
array
(
    [2135] => doe
    [3245] => smith
    [5342] => jones
    [5623] => doe
)