wpdb::get_col_info() │ public │ WP 0.71

Retrieves column metadata from the last query.

Method of the class: wpdb{}

Uses: wpdb::load_col_info()

No Hooks.

Return

Mixed. Column results.

Usage

global $wpdb;
$wpdb->get_col_info( $info_type, $col_offset );
$info_type(string)
Possible values include 'name', 'table', 'def', 'max_length', 'not_null', 'primary_key', 'multiple_key', 'unique_key', 'numeric', 'blob', 'type', 'unsigned', 'zerofill'.
Default: 'name'
$col_offset(int)
0: col name. 1: which table the col's in. 2: col's max length.
3: if the col is numeric. 4: col's type.
Default: -1

Examples

0

#1 Demo of work

Let's make a query:

global $wpdb;

$results = $wpdb->get_results( "SELECT * FROM $wpdb->postmeta" );

Now let's get the data about the table columns of this query:

$cols_data = $wpdb->get_col_info( 'name' );
/*
Array
(
	[0] => meta_id
	[1] => post_id
	[2] => meta_key
	[3] => meta_value
)
*/

$cols_data = $wpdb->get_col_info( 'max_length' );
/*
Array
(
	[0] => 6
	[1] => 5
	[2] => 45
	[3] => 20205
)
*/

$cols_data = $wpdb->get_col_info( 'type' );
/*
Array
(
	[0] => 8
	[1] => 8
	[2] => 253
	[3] => 252
)
*/

What happens if you specify a column name that does not exist:

$cols_data = $wpdb->get_col_info( 'primary_key' );
/*
Notice: Undefined property: stdClass::$primary_key in /wpexample.com/public_html/wp-includes/wp-db.php on line 3435
Notice: Undefined property: stdClass::$primary_key in /wpexample.com/public_html/wp-includes/wp-db.php on line 3435
Notice: Undefined property: stdClass::$primary_key in /wpexample.com/public_html/wp-includes/wp-db.php on line 3435
Notice: Undefined property: stdClass::$primary_key in /wpexample.com/public_html/wp-includes/wp-db.php on line 3435

Array
(
	[0] =>
	[1] =>
	[2] =>
	[3] =>
)
*/

To get the data of an individual column, you need to specify its index in the second parameter:

echo $wpdb->get_col_info( 'name', 0 );       //> meta_id
echo $wpdb->get_col_info( 'name', 1 );       //> post_id
echo $wpdb->get_col_info( 'max_length', 0 ); //> 6
echo $wpdb->get_col_info( 'max_length', 1 ); //> 5

Changelog

Since 0.71 Introduced.

wpdb::get_col_info() code WP 6.8

wp-includes/class-wpdb.php 
public function get_col_info( $info_type = 'name', $col_offset = -1 ) {
	$this->load_col_info();

	if ( $this->col_info ) {
		if ( -1 === $col_offset ) {
			$i         = 0;
			$new_array = array();
			foreach ( (array) $this->col_info as $col ) {
				$new_array[ $i ] = $col->{$info_type};
				++$i;
			}
			return $new_array;
		} else {
			return $this->col_info[ $col_offset ]->{$info_type};
		}
	}
}

wpdb