<form action="search2.php" method="GET">
<input type="text" name="requete" size="50" value="machin" onfocus="if(this.value='machin') { this.value='' }" onblur="if(this.value='') { this.value='machin' }">
<?php
session_start();
$_SESSION['requete']=htmlentities($_GET['requete']);
if (isset($_SESSION['requete'])){
$requete=$_SESSION['requete'];}
else {$requete = (htmlspecialchars($_GET['requete']));
header("location:/search2-".$requete.'.html');}
?>
RewriteRule ^search2-([a-zA-Z0-9\-]+).html$ /search2.php?requete=$1 [L]