max_allowed_packet
is set in mysql config, not on php side
[mysqld]
max_allowed_packet=16M
You can see it’s curent value in mysql like this:
SHOW VARIABLES LIKE 'max_allowed_packet';
You can try to change it like this, but it’s unlikely this will work on shared hosting:
SET GLOBAL max_allowed_packet=16777216;
You can read about it here http://dev.mysql.com/doc/refman/5.1/en/packet-too-large.html
EDIT
The [mysqld] is necessary to make the max_allowed_packet
working since at least mysql version 5.5.
Recently setup an instance on AWS EC2 with Drupal and Solr Search Engine, which required 32M max_allowed_packet
. It you set the value under [mysqld_safe]
(which is default settings came with the mysql installation) mode in /etc/my.cnf, it did no work. I did not dig into the problem. But after I change it to [mysqld]
and restarted the mysqld, it worked.