Possible problems and solutions after MySQL server upgrade

If you encounter an error message similar to the following during the operation that you want to perform on the MySQL server:

Field 'field_name' doesn't have a default value

Then we recommend that you run the following query after building a MySQL connection:

Up to PHP version 5.7 you should use the following code:

mysql_query("SET SESSION sql_mode = ''");

From PHP version 7.0 or higher, you should use the following line of code:

mysqli_query("SET SESSION sql_mode = ''");