You will likely want to do something like this:
$ctr = 0;
$matchcode = '';
$parts=array_map('trim',explode(' ',$keyword));
while(count($parts)>0){
$parts = array_reverse($parts);
$part=array_pop($parts);
$ctr++;
if($ctr == 1){
$matchcode .= "`sbody` LIKE '%$part%' OR `stitle` LIKE '%$part%' OR `sdescription` LIKE '%$part%'";
}
else {
$matchcode .= " OR `sbody` LIKE '%$part%' OR `stitle` LIKE '%$part%' OR `sdescription` LIKE '%$part%'";
}
}
$sql = "SELECT `sid`, `sbody`, `stitle`, `sdescription` FROM `simple_search` WHERE " . $matchcode . " ORDER BY `stitle`";