如何在搜索中添加其他关键字？

<form action="search.php" method="post" class="search" id="search">
     <input name="search" id="search" type="text" value=""><br>
</form>
...
echo ".urlencode($_POST['search']).";

here is my basic search box. I want: 1. open the page first, the ".urlencode($_POST['search'])." is empty. 2. when the client type some word and make a search, the ".urlencode($_POST['search'])." will always add a additional keyword after client type word.

for example, when the client type: apple, the ".urlencode($_POST['search'])." part show: apple20%juice, when the client type: orange, the ".urlencode($_POST['search'])." part show: orange20%juice, it always add a additional keyword 20%juice behind the key word.

How to reach this one? Thanks.

like this:

check if the search is set first if so go ahead and grab the string and add juice to it

if(isset($_POST['search']))
{
  $searchterm = $_POST['search']." juice";
  //follw by other stmts...
}

Couldn't you simply use;

print urlencode($_POST['search'].' juice');