MySQL, CONCAT, the result is null after a while -

im putting big data table, longblob field, table grows, field becomes empty. code:

mysql_query ('create table if not exists testtable (content longblob not null) engine = myisam'); mysql_query('truncate table testtable'); mysql_query('replace testtable values (".")'); $bigdata = str_repeat('a', 1024*1024*2); // 2 mb! foreach (str_split($bigdata, 1024*64) $item) {     mysql_query ('update testtable set content = concat(content, "'.mysql_real_escape_string($item).'")');     $rec = mysql_fetch_row(mysql_query ('select content testtable'));     echo 'size of content: '.strlen($rec[0]).'<br>'; } 

the output:

size of content: 65537 size of content: 131073 size of content: 196609 size of content: 262145 size of content: 327681 size of content: 393217 size of content: 458753 size of content: 524289 size of content: 589825 size of content: 655361 size of content: 720897 size of content: 786433 size of content: 851969 size of content: 917505 size of content: 983041 size of content: 0 size of content: 65536 size of content: 131072 size of content: 196608 

whats happening? longblob should take more data that.

increase max_allowed_packet size.

it looks failing @ 1mb, , according https://dev.mysql.com/doc/refman/5.5/en/packet-too-large.html default max packet size 1mb:

the server's default max_allowed_packet value 1mb. can increase if server needs handle big queries

set value in my.cnf file, e.g.:

[mysqld] max_allowed_packet=16m 

in php

if don't have access mysql config try setting via query (note: i've not checked if work).

$db->query( 'set @@global.max_allowed_packet = 16777216' );