note 31173 added to function.eregi

trying to validate a UK post code ie. kt1 2ls and used the following to do so eregi("^([[:alnum:]]{3,4})+(| )+([[:alnum:]]{3,4})$" where(| ) corresponds to the space between 2 alphanumeric items but this error message appears Warning: eregi() [function.eregi]: REG_EMPTY is there anyway to check for a space in the text entered? (only one space though) -- http://www.php.net/manual/en/function.eregi.php http://master.php.net/manage/user-notes.php?action=edit+31173 http://master.php.net/manage/user-notes.php?action=delete+31173 http://master.php.net/manage/user-notes.php?action=reject+31173