WordPress at a glance
function is not described

post_custom() WP 1.5.0

Retrieve post custom meta data field.

No Hooks.

Return

false/String/Array. Array of values or single value, if only one element exists. False will be returned if key does not exist.

Usage

post_custom( $key );
$key(string)
Meta data key name.
Default: ''

Code of post custom: wp-includes/post-template.php VER 5.1.1

<?php
function post_custom( $key = '' ) {
	$custom = get_post_custom();

	if ( ! isset( $custom[ $key ] ) ) {
		return false;
	} elseif ( 1 == count( $custom[ $key ] ) ) {
		return $custom[ $key ][0];
	} else {
		return $custom[ $key ];
	}
}