Inp1=document.NAME_DES_FORMULARS.NAME_VON_INPUT_1.value;
   Inp2=document.NAME_DES_FORMULARS.NAME_VON_INPUT_2.value;

   if (Inp1!='')   // wenn Inp1 NCHT leer, dann ...
   {
      ...
   }

   if (Inp1==Inp2) // wenn Inhalt gleich, dann ...
   {
      ...
   }

<form name="Formular" action="inhalt/fu_handleform.php" method="post">  <input type="text" name="Array[textfeld1]" size="20">
  <input type="text" name="Array[textfeld2]" size="20">
</form>

$Array["textfeld1"] = trim
($Array["textfeld1"]);

$Host = "#";
$User = "#";
$Password = "#";
$DBName = "#";
$TableName = "#";

$Link = mysql_connect ($Host, $User, $Password);
$Query = "Insert into $TableName values ('0', '$Array[textfeld1]',";

print ("The query is:
$Query

\n");
if (mysql_db_query ($DBName, $Query, $Link)) {
print ("The query was successfully executed!
\n");
} else {
print ("The query could not be executed!
\n");
}

mysql_close ($Link);