Bingung dengan Perintah/Syntax PHP5

Dok, sbenernya perintah/syntax di PHP5 selain $_SERVER, $_GET, $_POST apa lg? Masalahnya gw dah coba edit script dari PHP4 ke PHP5 masih susah. Emang sih ada trik untuk membuat fungsi otomatis tanpa mengubah code. Tp saya kira alangkah lebihbaiknya mengubah code jadi sekalian belajar PHP5. Ini dok contoh scriptnya syntax apa aja yg harus diubah agar jalan di register_global off?? ini salah satu sample script yg saya maksudkan karna mayoritas codingnya spt itu menggunakan switch. trm ksh dok.

Code:

<?
if(ereg("aminz_ym.php",$_SERVER[PHP_SELF]))
{header("location:index.php");
die; }

if(!session_is_registered('id')){
header("location:index.php");
}
echo "<div id=\"center_content\" class=\"sidebar\">
<div class=\"content_top_sub\"><table width=100% cellspacing=0 cellpadding=0 border=0><tr><td height=30><b>Admin Yahoo Messenger</b></td></tr></table></div>
<div class=\"content_center\">
";

echo "<strong>Yahoo Messenger!</strong><p>";
include "aminz_ym_menu.php";

function index(){
include "koneksi.php";
include "include/zetting.php";
//Rumus pagination
$batas=10;
$halaman=$_GET['halaman'];
if(empty($halaman))
{
$posisi=0;
$halaman=1;
}
else
{
$posisi = ($halaman-1) * $batas;
}
$no=$posisi+1;

$perintah = "SELECT * FROM $tbl_ym order by idym LIMIT $posisi,$batas";
$hasil = mysql_query( $perintah);
$warna="class=formulir";
echo "<TABLE width=100% cellspacing=1 cellpadding=4>";
while ($data = mysql_fetch_row($hasil)) {
$idym = $data[0];
$nama = $data[1];
$username= $data[2];

$wcell = (!$wcell)?"$warna":'';

echo "<tr class=menubg1><td>Nama : <a href=$_SERVER[PHP_SELF]?ipdCMS=aminz_ym&mode=edit&idym=$idym>$nama</a><br>ID YM : $username<br></td>";
echo "<td><a href=$_SERVER[PHP_SELF]?ipdCMS=aminz_ym&mode=del&idym=$idym>Hapus</a> - <a href=$_SERVER[PHP_SELF]?ipdCMS=aminz_ym&mode=edit&idym=$idym>Edit</a></td></tr>";
$no++;

}
echo "</TABLE>";

$file = "$_SERVER[PHP_SELF]?ipdCMS=aminz_ym&mode=index";

//Langkah 3: Hitung total data dan halaman
$tampil2="select * from $tbl_ym";
$hasil2=mysql_query($tampil2);
$jmldata=mysql_num_rows($hasil2);

$jmlhalaman=ceil($jmldata/$batas);

// Link ke halaman sebelumnya (previous)
echo "<table width=98% align=center cellspacing=1 cellpadding=1 border=0><tr><td align=center><br><hr size=1>";
if($halaman > 1){
$previous=$halaman-1;
echo "<A HREF='$file&idym=$idym&halaman=1'><< Awal</A> |
<A HREF='$file&idym=$idym&halaman=$previous'><< Sebelumnya</A> | ";
}
else
{
echo "<< Awal | < Sebelumnya | ";
}

// Tampilkan link halaman 1,2,3 ...
for($i=1;$i<=$jmlhalaman;$i++)
if ($i != $halaman){
echo " <a href='$file&idym=$idym&halaman=$i'>$i</A> | ";
}
else{
echo " <b><font color=red>$i</font></b> | ";
}

// Link kehalaman berikutnya (Next)
if($halaman < $jmlhalaman){
$next=$halaman+1;
echo "<A HREF='$file&idym=$idym&halaman=$next'>Selanjutnya ></A> |
<A HREF='$file&idym=$idym&halaman=$jmlhalaman'>Terakhir >></A> ";
}
else{
echo "Selanjutnya > | Terakhir >>";
}
echo "</td></tr></table>";

}

function add($submit,$nama,$idym){
include "koneksi.php";
include "include/zetting.php";

if ($_POST[submit]) {

$perintah="INSERT INTO $tbl_ym (nama,username) VALUES ('$nama','$username')";
$hasil = mysql_query( $perintah );

echo "<table width=100% cellspacing=0 cellpadding=0><tr><td class=td_1> <b>YM baru telah ditambahkan!</b></td></tr></table>";

echo"<p><a href=$_SERVER[PHP_SELF]?ipdCMS=aminz_ym&mode=index>:: Klik Disini ::</a></p>";
} else {
?>
<table width=100% cellspacing=0 cellpadding=0><tr><td class=td_1> <b>Tambah YM!</b></td></tr></table>

<form method=post action='<? echo $_SERVER[PHP_SELF];?>?ipdCMS=aminz_ym'>
<table class=formulir>
<tr>
<td valign=top>Nama</td>
<td valign=top>
<input type=hidden name=mode value="add">
<input type=text size=30 name=nama> (Nama Panggilan Anda / Nickname)</td>
</tr>
<tr>
<td valign=top>ID YM</td>
<td valign=top><input type=text size=30 name=username value="<? echo "$username"; ?>"> <br>(Misalkan Email Anda : coband83@yahoo.com! Maka id YM anda adalah -> <b>coband83</b>!)</td>
</tr>
<tr>
<td colspan=2><input type=submit name=submit value=Tambah></td>
</tr>
</table>
</form>
<?
}
}

function update($idym, $nama, $username, $submit) {
include "koneksi.php";
include "include/zetting.php";

if ($submit) {

if (!$nama or !$username) {
$salah = "<span style=\"font-weight:bold;color:red\"> Formulir belum terisi dengan benar, silahkan ulangi.</span><p><a href=$_SERVER[PHP_SELF]?ipdCMS=aminz_ym\"javascript:history.back()\"><< Kembali</a>";
echo $salah;
//include "themes/$theme/footer.php";
exit;
}

$perintah="UPDATE $tbl_ym SET nama='$nama', username='$username' WHERE idym='$idym'";
$hasil = mysql_query( $perintah );

echo "<table width=100% cellspacing=0 cellpadding=0><tr><td class=td_1> <b>YM telah diedit!</b></td></tr></table>";

echo"<p><a href=$_SERVER[PHP_SELF]?ipdCMS=aminz_ym&mode=index>:: Klik Disini ::</a></p>";
}
}

function edit($idym){
include "koneksi.php";
include "include/zetting.php";

$perintah="SELECT * FROM $tbl_ym WHERE idym=$idym";
$hasil = mysql_query( $perintah );
while ($data = mysql_fetch_row($hasil)) {
$idym=$data[0];
$nama=$data[1];
$username=$data[2];
}

?>
<table width=100% cellspacing=0 cellpadding=0><tr><td class=td_1> <b>Manajemen Yahoo Messenger</b></td></tr></table>

<form method=post action='<? echo $_SERVER[PHP_SELF];?>?ipdCMS=aminz_ym'>
<table class=formulir>
<tr>
<td>Nama</td>
<td>
<input type=hidden name=idym value="<? echo "$idym"; ?>">
<input type=hidden name=mode value="update">
<input type=text size=30 name=nama value="<? echo "$nama"; ?>"></td>
</tr>
<tr>
<td>Username</td>
<td><input type=text size=30 name=username value="<? echo "$username"; ?>"></td>
</tr>
<tr>
<td> </td>
<td>Misalkan Email Anda : <br><b>coband83@yahoo.com / coband83@yahoo.co.id<br>
(Anda cukup menuliskan UserID saja -> coband83)</b></td>
</tr>
<tr>
<td colspan=2><input type=submit name=submit value=Edit></td>
</tr>
</table>
</form>
<?
}

function hapus($idym){
include "koneksi.php";
include "include/zetting.php";

mysql_query("DELETE FROM $tbl_ym WHERE idym='$idym'");
echo "<table width=100% cellspacing=0 cellpadding=0><tr><td class=td_1> <b>YM telah dihapus!</b></td></tr></table>";

echo" <p><a href=$_SERVER[PHP_SELF]?ipdCMS=aminz_ym&mode=index>:: Klik Disini ::</a>";
}

if(!isset($mode))$mode='';
switch($mode){
case 'index':
index();
break;
case 'del':
hapus($idym);
break;
case 'edit':
edit($idym);
break;
case 'add':
add($submit,$nama,$username);
break;
case 'update':
update($idym, $nama, $username, $submit);
break;

}
echo "
</div>
<div class=\"content_bottom_topic\"></div>

</div>
";
?>