Hint=0 はすでに定義されていますが、なぜ if(hint=0) が必要なのでしょうか?

<?php$xmlDoc = new DOMDocument();$xmlDoc->load("links.xml");$x=$xmlDoc->getElementsByTagName('link');//get the q parameter from URL$q=$_GET["q"];//lookup all links from the xml file if length of q>0if (strlen($q) > 0){$hint="";for($i=0; $i<($x->length); $i++) { $y=$x->item($i)->getElementsByTagName('title'); $z=$x->item($i)->getElementsByTagName('url'); if ($y->item(0)->nodeType==1)  {  //find a link matching the search text  if (stristr($y->item(0)->childNodes->item(0)->nodeValue,$q))   {   if ($hint=="")    {    $hint="<a href='" .     $z->item(0)->childNodes->item(0)->nodeValue .     "' target='_blank'>" .     $y->item(0)->childNodes->item(0)->nodeValue . "</a>";    }   else    {    $hint=$hint . "<br /><a href='" .     $z->item(0)->childNodes->item(0)->nodeValue .     "' target='_blank'>" .     $y->item(0)->childNodes->item(0)->nodeValue . "</a>";    }   }  } }}// Set output to "no suggestion" if no hint were found// or to the correct valuesif ($hint == "") { $response="no suggestion"; }else { $response=$hint; } //output the responseecho $response;?>

if ($hint=="")    {    $hint="<a href='" .     $z->item(0)->childNodes->item(0)->nodeValue .     "' target='_blank'>" .     $y->item(0)->childNodes->item(0)->nodeValue . "</a>";    }   else    {    $hint=$hint . "<br /><a href='" .     $z->item(0)->childNodes->item(0)->nodeValue .     "' target='_blank'>" .     $y->item(0)->childNodes->item(0)->nodeValue . "</a>";    }