SELECT(MAX) not going past 10 - mysql with phpmyadmin -

i'm creating php script insert rows database called orders based on shopping cart stored in associative array using sessional array $_session['cart']. database looks this:

orders ----------+--------------+-------------+-------------+-------------+    id     |   username   |   item1id   |   item2id   |   item3id   | ----------+--------------+-------------+-------------+-------------+ 1         | a@aa.com     |   8000001   |   8000002   |   800003    | ----------+--------------+-------------+-------------+-------------+ 5         | a@aa.com     |   7000001   |   6000002   |   700003    | ----------+--------------+-------------+-------------+-------------+ 7         | b@bb.com     |   8000001   |   8000002   |    null     | ----------+--------------+-------------+-------------+-------------+ 10        | a@aa.com     |   3000001   |   1000002   |   800009    | ----------+--------------+-------------+-------------+-------------+ 

id column type char(20) may choose use letters later on.

as part of inserting row, need assign id (primary key) order row set 1 higher current highest id number found.

the whole script works perfectly; query finds highest id in table , increment 1 , assign variable use part of insert query. problem "select max(id) orders" can't seem find higher 9. there condition prevents select max(id) identifying in double digits?

i've got written like:

$highestid = mysqli_query($conn, "select max(id) orders");  $orderid = $highestid +1; 

i've emptied database except id numbers1 , 2. running php script inserts new rows id numbers 3, 4, 5 except when gets 10, script unable produces error of having duplicate primary key of '10' (from $orderid's value). when manually entering row database id of '25', $orderid still returns '10' when echo out result.

i have not set specific limits amount of rows can entered or that.

you not need go through trouble auto-incremental pk. here's how can go it.

step 1 : in phpmyadmin, edit table, , check a_i checkbox pk column.

step 2 : while inserting php, leave field blank. automatically assign value of current max + 1 pk.

eg,

$query = "insert mytable (id, name) values ('', 'name1'), ('', 'name2')"; 

edit : cannot have char(20) pk , expect increment work btw.