Connection With database Got an error Reading Communication Packets - php

Question

I've migrated a Database from cPanel to cPanel through Backup tool, But the problem is whenever i try to connect to this database for example using this TEST php code
<?php
# Fill our vars and run on cli
# $ php -f db-connect-test.php
$dbname = 'imadoulh_test';
$dbuser = 'xxxxx';
$dbpass = 'xxxxx';
$dbhost = 'localhost';
$connect = mysql_connect($dbhost, $dbuser, $dbpass) or die("Unable to Connect to '$dbhost'");
mysql_select_db($dbname) or die("Could not open the db '$dbname'");
$test_query = "SHOW TABLES FROM $dbname";
$result = mysql_query($test_query);
$tblCnt = 0;
while($tbl = mysql_fetch_array($result)) {
$tblCnt++;
#echo $tbl[0]."<br />\n";
}
if (!$tblCnt) {
echo "There are no tables<br />\n";
} else {
echo "There are $tblCnt tables<br />\n";
}
the response is This page isn’t working with HTTP ERROR 500
and the MySQL log says Got an error reading communication packets
I did try many ways to fix it but unfortunately.
Here's what I tried:
1. optimize and repair tables
2. add some code to /etc/my.conf file such as
max_allowed_packet=2684354569944
open_files_limit=10000
default-storage-engine=MyISAM
innodb_file_per_table=1
default_authentication_plugin=mysql_native_password
dealing with this article:
https://dba.stackexchange.com/questions/19135/mysql-error-reading-communication-packets

Answer 1

Error 500 from http means your web program -- your php program -- failed trying to send out that page. But 500 can tell us absolutely nothing about why it failed. So, moving along... You seem to be getting communication errors between php and mysql.
I believe the key words in your question are from cPanel to cPanel. That suggests you are migrating your application from server to server and maybe even from hosting-vendor to hosting-vendor.
You have imported your MySQL data from backups onto a new server with a different IP address. So, you now have two different database instances. And, it's possible you have two different instances of your php program.
So now you're troubleshooting these questions:
Can my new php code talk to my new database server? From your question it's hard to tell whether the answer is "no" or "sometimes, but unreliably."
Does my new php code run at the same hosting vendor as its MySQL database? In network engineer lingo the question is "are they on the same datacenter network?"
Is there any chance I'm trying to hit the new database from the old code, or the old database from the new code?
Some (but not all) technical support specialists at hosting companies know about this kind of thing. Call for help, but be sure the first two words out of your mouth are "I'm migrating" so they know it's a new customer and a one-time setup issue.