PHP array assigned with and

Question

Just learning php and looking into someone else's code. I'm not sure what is happening in this function with the word 'and' on the left side of the = operator. It seems like it is a 'silent' if is being used eg. if $arry =true and $array2 = true then $array2 += 'somthing';

I cant seem to find any reference to this anywhere online.

  function get_list_filter($filter = array()) {
     global $current_user;
    $sql = array();
    $filter["clientID"]         and $sql[] = sprintf("(WD_domain.clientID = %d)",$filter["clientID"]);
    $filter["showDomainName"]   and $sql[] = sprintf("(WD_domain.domain LIKE '%%%s%%')",$filter["showDomainName"]);
    $filter["showManaged"]      and $sql[] = sprintf("(WD_domain.managed = %d)",$filter["showManaged"]);
    return $sql;
  }

Answer 1

$foo and $bar = "baz";

Is just a confusing way of saying

if ($foo)
    $bar = "baz";

Shame on whoever wrote that.

Answer 2

It means that if the left side of the and evaluates to true, the right side will be executed also. In essence, if clientID evaluates to true (is non-false), then sprintf("(WD_domain.clientID = %d)",$filter["clientID"]) will be added to the $sql array.

It's a lazy way of doing this:

if($filter["clientID"]) {
    $sql[] = sprintf("(WD_domain.clientID = %d)",$filter["clientID"]);
}