[Resolved] Mysql Foreign Key question

In my php web aplication i do need to
simulate an auto_increment field
(because i can not have two auto fields on the same table)

I my research i found this code :

SELECT @NextId := (MAX(id)+1) FROM Table
INSERT INTO Table (id) VALUES (@NextId)

what is the @NextId ?
why is it assigned with this operand := ?
Is it a mysql variable?
can i receive this value in a php variable?

Thank´s in advance

what is the @NextId ?

mysql user variable

why is it assigned with this operand := ?

Because that is mysql's syntax

Is it a mysql variable?

see 1

can i receive this value in a php variable?

if you want the next id as a php variable

$res = mysql_query("SELECT MAX(id)+1 FROM mytable);
$nextid = mysql_result($res, 0);

hth

Thanks a lot
Greetings