array_column() 返回input数组中键值为column_key的列， 如果指定了可选参数index_key，那么input数组中的这一列的值将作为返回数组中对应值的键。
参数
input
需要取出数组列的多维数组（或结果集）
column_key
需要返回值的列，它可以是索引数组的列索引，或者是关联数组的列的键。 也可以是NULL，此时将返回整个数组（配合index_key参数来重置数组键的时候，非常管用）
index_key
作为返回数组的索引/键的列，它可以是该列的整数索引，或者字符串键值。
返回值
从多维数组中返回单列数组
范例
Example #1 从结果集中取出first names列
<?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);
?>
以上例程会输出：
Array
(
[0] => John
[1] => Sally
[2] => Jane
[3] => Peter
)
Example #2 从结果集中总取出last names列，用相应的id作为键值
<?php
// Using the $records array from Example #1
$last_names = array_column($records, 'last_name', 'id');
print_r($last_names);
?>
以上例程会输出：
Array
(
[2135] => Doe
[3245] => Smith
[5342] => Jones
[5623] => Doe
)
如果你的php版本没有array_column函数，那么可以用一下代码代替：
<?php
/**
* This file is part of the array_column library
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*
* @copyright Copyright (c) Ben Ramsey (http://benramsey.com)
* @license http://opensource.org/licenses/MIT MIT
*/
if (!function_exists('array_column')) {
/**
* Returns the values from a single column of the input array, identified by
* the $columnKey.
*
* Optionally, you may provide an $indexKey to index the values in the returned
* array by the values from the $indexKey column in the input array.
*
* @param array $input A multi-dimensional array (record set) from which to pull
* a column of values.
* @param mixed $columnKey The column of values to return. This value may be the
* integer key of the column you wish to retrieve, or it
* may be the string key name for an associative array.
* @param mixed $indexKey (Optional.) The column to use as the index/keys for
* the returned array. This value may be the integer key
* of the column, or it may be the string key name.
* @return array
*/
function array_column($input = null, $columnKey = null, $indexKey = null)
{
// Using func_get_args() in order to check for proper number of
// parameters and trigger errors exactly as the built-in array_column()
// does in PHP 5.5.
$argc = func_num_args();
$params = func_get_args();
if ($argc < 2) {
trigger_error("array_column() expects at least 2 parameters, {$argc} given", E_USER_WARNING);
return null;
}
if (!is_array($params[0])) {
trigger_error(
'array_column() expects parameter 1 to be array, ' . gettype($params[0]) . ' given',
E_USER_WARNING
);
return null;
}
if (!is_int($params[1])
&& !is_float($params[1])
&& !is_string($params[1])
&& $params[1] !== null
&& !(is_object($params[1]) && method_exists($params[1], '__toString'))
) {
trigger_error('array_column(): The column key should be either a string or an integer', E_USER_WARNING);
return false;
}
if (isset($params[2])
&& !is_int($params[2])
&& !is_float($params[2])
&& !is_string($params[2])
&& !(is_object($params[2]) && method_exists($params[2], '__toString'))
) {
trigger_error('array_column(): The index key should be either a string or an integer', E_USER_WARNING);
return false;
}
$paramsInput = $params[0];
$paramsColumnKey = ($params[1] !== null) ? (string) $params[1] : null;
$paramsIndexKey = null;
if (isset($params[2])) {
if (is_float($params[2]) || is_int($params[2])) {
$paramsIndexKey = (int) $params[2];
} else {
$paramsIndexKey = (string) $params[2];
}
}
$resultArray = array();
foreach ($paramsInput as $row) {
$key = $value = null;
$keySet = $valueSet = false;
if ($paramsIndexKey !== null && array_key_exists($paramsIndexKey, $row)) {
$keySet = true;
$key = (string) $row[$paramsIndexKey];
}
if ($paramsColumnKey === null) {
$valueSet = true;
$value = $row;
} elseif (is_array($row) && array_key_exists($paramsColumnKey, $row)) {
$valueSet = true;
$value = $row[$paramsColumnKey];
}
if ($valueSet) {
if ($keySet) {
$resultArray[$key] = $value;
} else {
$resultArray[] = $value;
}
}
}
return $resultArray;
}
}