php5.5新数组函数array_column使用_PHP教程

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

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)

// 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
)// 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
)

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