WordPress at a glance
function is not described

_usort_by_first_member() WP 2.9.0

Sorts a multidimensional array by first member of each top level member

Used by uasort() as a callback, should not be used directly.

No Hooks.

Return

Int.

Usage

_usort_by_first_member( $a, $b );
$a(array) (required)
$b(array) (required)

Code of usort by first member: wp-admin/includes/import.php VER 5.0.3

<?php
function _usort_by_first_member( $a, $b ) {
	return strnatcasecmp( $a[0], $b[0] );
}