[Carpetsmoker]

It's a PHP setting in /usr/local/etc/php.ini

; Maximum allowed size for uploaded files.
upload_max_filesize = 2M

; Maximum size of POST data that PHP will accept.
post_max_size = 8M

It's also possible limits are set in login.conf, but the php.ini is more common.

There are two things you can do:
1) Change the php.ini file if you have access to it.
2) Don't read the entire file at once, for example:

$fp = fopen('myfile.csv', 'r');
while ($line = fgets($fp))
{
  print $line;
}
fclose($fp)