Membuat Kode Otomatis (Auto Number) di PHP

<?php
//kode otomatis
$sql="select `id_client` from `$tbclient` order by `id_client` desc";
$jum= getJum($conn,$sql);
$kd="CLN";
if($jum > 0){
$d=getField($conn,$sql);
$idmax=$d['id_client'];
$urut=substr($idmax,3,3)+1;//01
if($urut<10){$idmax="$kd"."00".$urut;}
else if($urut<100){$idmax="$kd"."0".$urut;}
else{$idmax="$kd".$urut;}
}
else{$idmax="$kd"."001";}
$id_client=$idmax;
?>

Kode Otomatis 2

<?php
$sql="select `id_order` from `$tborder` order by `id_order` desc";
$q=mysqli_query($conn, $sql);
$jum=mysqli_num_rows($q);
$th=date("y");
$bl=date("m")+0;if($bl<10){$bl="0".$bl;}

$kd="ORD".$th.$bl;//KEG1610001
if($jum > 0){
$d=mysqli_fetch_array($q);
$idmax=$d["id_order"];

$bul=substr($idmax,5,2);
$tah=substr($idmax,3,2);
if($bul==$bl && $tah==$th){
$urut=substr($idmax,7,3)+1;
if($urut<10){$idmax="$kd"."00".$urut;}
else if($urut<100){$idmax="$kd"."0".$urut;}
else{$idmax="$kd".$urut;}
}//==
else{
$idmax="$kd"."001";
}
}//jum>0
else{$idmax="$kd"."001";}
$id_order=$idmax;

?>

Kode Otomatis 3

<?php
$sql="select `id_admin` from `$tbadmin` order by `id_admin` desc";
$jum= getJum($conn,$sql);
$kd="ADM";
if($jum > 0){
$d=getField($conn,$sql);
$idmax=$d['id_admin'];
$urut=substr($idmax,3,2)+1;//01
if($urut<10){$idmax="$kd"."0".$urut;}
else{$idmax="$kd".$urut;}
}
else{$idmax="$kd"."01";}
$id_admin=$idmax;

?>