array_column

(PHP 5 >= 5.5.0)

array_columnReturn the values from a single column in the input array

Description

array array_column ( array $array , mixed $column_key [, mixed $index_key = null ] )

array_column() returns the values from a single column of the array, identified by the column_key. Optionally, you may provide an index_key to index the values in the returned array by the values from the index_key column in the input array.

Parameters

array

A multi-dimensional array (record set) from which to pull a column of values.

column_key

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. It may also be NULL to return complete arrays (useful together with index_key to reindex the array).

index_key

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 Values

Returns an array of values representing a single column from the input array.

Examples

Example #1 Get column of first names from recordset

<?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);
?>

The above example will output:

Array
(
    [0] => John
    [1] => Sally
    [2] => Jane
    [3] => Peter
)

Example #2 Get column of last names from recordset, indexed by the "id" column

<?php
// Using the $records array from Example #1
$last_names array_column($records'last_name''id');
print_r($last_names);
?>

The above example will output:

Array
(
    [2135] => Doe
    [3245] => Smith
    [5342] => Jones
    [5623] => Doe
)

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User Contributed Notes 2 notes

up
19
WARrior
1 year ago
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)
up
0
myles at smyl dot es
1 day ago
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' ) ) {
    /**
     * Returns the values recursively from columns 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_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;
    }
}
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