array_column

(PHP 5 >= 5.5.0, PHP 7)

array_column — 返回数组中指定的一列

说明

array array_column ( array $input , mixed $column_key [, mixed $index_key ] )

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
)

用户评论:

[#1] antonfedonjuk at gmail dot com [2015-07-21 18:26:48]

My version is closer to the original than http://github.com/ramsey/array_column
<?php if (!function_exists('array_column')) { function array_column(array $array, $columnKey, $indexKey = null) { $result = array(); foreach ($array as $subArray) { if (!is_array($subArray)) { continue; } elseif (is_null($indexKey) && array_key_exists($columnKey, $subArray)) { $result[] = $subArray[$columnKey]; } elseif (array_key_exists($indexKey, $subArray)) { if (is_null($columnKey)) { $result[$subArray[$indexKey]] = $subArray; } elseif (array_key_exists($columnKey, $subArray)) { $result[$subArray[$indexKey]] = $subArray[$columnKey]; } } } return $result; } } ?>

[#2] till at etill dot net [2015-05-28 15:32:59]

Some remarks not included in the official documentation.

1) array_column does not support 1D arrays, in which case an empty array is returned.

2) The $column_key is zero-based.

3) If $column_key extends the valid index range an empty array is returned.

[#3] marianbucur17 at yahoo dot com [2015-05-18 06:19:16]

If array_column is not available you can use the following function, which also has the $index_key parameter:

if (!function_exists('array_column')) {
    function array_column($array, $column_key, $index_key = null)
    {
        return array_reduce($array, function ($result, $item) use ($column_key, $index_key)
        {
            if (null === $index_key) {
                $result[] = $item[$column_key];
            } else {
                $result[$item[$index_key]] = $item[$column_key];
            }

            return $result;
        }, []);
    }
}

[#4] mohanrajnr at gmail dot com [2015-05-06 07:50:52]

if array_column does not exist the below solution will work.

if(!function_exists("array_column"))
{

    function array_column($array,$column_name)
    {

        return array_map(function($element) use($column_name){return $element[$column_name];}, $array);

    }

}

[#5] robbieaverill[at]gmail.com [2015-03-23 19:51:27]

Another option for older PHP versions (pre 5.5.0) is to use array_walk():

<?php $array = array( array('some' => 'var', 'foo' => 'bar'), array('some' => 'var', 'foo' => 'bar'), array('some' => 'var', 'foo' => 'bar') ); array_walk($array, function(&$value, $key, $return) { $value = $value[$return]; }, 'foo'); print_r($array); // Array // ( // [0] => bar // [1] => bar // [2] => bar // ) ?>

[#6] kiler129 @ nowhere [2015-01-10 02:31:20]

Please note this function accepts 2D-arrays ONLY, and silently returns empty array when non-array argument is provided.

Code:
class testObject {
public $a = 123;
}
$testArray = [new testObject(), new testObject(), new testObject()];
$result = array_column($testArray, 'a')); //array(0) { }

[#7] hypxm at qq dot com [2014-12-09 06:36:03]

a simple solution:

function arrayColumn(array $array, $column_key, $index_key=null){
        if(function_exists('array_column ')){
            return array_column($array, $column_key, $index_key);
        }
        $result = [];
        foreach($array as $arr){
            if(!is_array($arr)) continue;

            if(is_null($column_key)){
                $value = $arr;
            }else{
                $value = $arr[$column_key];
            }

            if(!is_null($index_key)){
                $key = $arr[$index_key];
                $result[$key] = $value;
            }else{
                $result[] = $value;
            }

        }

        return $result;
    }

[#8] coviex [2014-11-30 16:53:00]

Value for existing key in the resulting array is rewritten with new value if it exists in another source sub-array.

[#9] myles at smyl dot es [2014-11-23 02:52:27]

This didn't work for me recursively and needed to come up with a solution.

Here's my solution to the function:

if ( ! function_exists( 'array_column_recursive' ) ) {

function array_column_recursive( $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 ( $argc < 2 ) {
trigger_error( "array_column_recursive() expects at least 2 parameters, {$argc} given", E_USER_WARNING );

return NULL;
}
if ( ! is_array( $params[ 0 ] ) ) {
// Because we call back to this function, check if call was made by self to
// prevent debug/error output for recursiveness :)
$callers = debug_backtrace();
if ( $callers[ 1 ][ 'function' ] != 'array_column_recursive' ){
trigger_error( 'array_column_recursive() 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_recursive(): 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_recursive(): 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 ];
}

$possibleValue = array_column_recursive( $row, $paramsColumnKey, $paramsIndexKey );
if ( $possibleValue ) {
$resultArray = array_merge( $possibleValue, $resultArray );
}

if ( $valueSet ) {
if ( $keySet ) {
$resultArray[ $key ] = $value;
} else {
$resultArray[ ] = $value;
}
}
}

return $resultArray;
}
}

[#10] WARrior [2013-10-03 12:25:11]

You can also use array_map fucntion if you haven't array_column().

example:

$a = array(
    array(
        'id' => 2135,
        'first_name' => 'John',
        'last_name' => 'Doe',
    ),
    array(
        'id' => 3245,
        'first_name' => 'Sally',
        'last_name' => 'Smith',
    )
);

array_column($a, 'last_name');

becomes

array_map(function($element){return $element['last_name'];}, $a);