How accurate is mysql_insert_id()??

ragedigital

I want to get the last ID inserted, but am concerned that it might be a race between my INSERT and another user INSERTing at the same time.

Is mysql_insert_id() extremely accurate?

Is there a better option?

Thanks,

darrin

NogDog

mysql_insert_id() will return the ID of the last insert query of the applicable mysql connection. As long as you are not using persistent connections, there is no way another user's insert would interfere, as they would be using a separate connection. If you are (or may be) using persistent connections, then you may need to use table locking to prevent anyone else from doing an insert until you have done yours and gotten the insert ID.

Feyd-Rautha

Hello,
this is the answer I was looking for 🙂

But I need to be sure about another doubt.

I was encouraged to use a singleton class to handle my database connection, like the one described Here

This method is cool, but It's not yet very clear to me what is the scope of such an object.
When it says that it will help me always use the same connection, does it refer to the single PHP request, or is the connection shared between all the pages that instantiate the object? In that case, mysql_insert_id() would return inconsistent data, wouldn't it?

jkurrle

One issue with mysql_insert_id() that may have been fixed, but I'm not sure. I remember there was an issue with using it with Big Integers (BigInt) as the counter. If you got above a certain number, it would break or something. When using BigInt instead of integer, this code is supposed to work correctly:

$result=mysql_query("select last_insert_id");
$row=mysql_fetch_row($result);
$trx_id=$row[0];

Again, this was a PHP4 issue, they probably fixed it in PHP5...

NogDog

Feyd-Rautha wrote:
Hello,
this is the answer I was looking for 🙂

But I need to be sure about another doubt.

I was encouraged to use a singleton class to handle my database connection, like the one described Here

This method is cool, but It's not yet very clear to me what is the scope of such an object.
When it says that it will help me always use the same connection, does it refer to the single PHP request, or is the connection shared between all the pages that instantiate the object? In that case, mysql_insert_id() would return inconsistent data, wouldn't it?

It would be unique only within the scope of the current script. Each separate call to the script would still have its own instance of that object.