WordPress Version: 4.3
/**
* Callback to add a target attribute to all links in passed content.
*
* @since 2.7.0
* @access private
*
* @global string $_links_add_target
*
* @param string $m The matched link.
* @return string The processed link.
*/
function _links_add_target($m)
{
global $_links_add_target;
$tag = $m[1];
$link = preg_replace('|( target=([\'"])(.*?)\2)|i', '', $m[2]);
return '<' . $tag . $link . ' target="' . esc_attr($_links_add_target) . '">';
}