a permanent way of doing mysqli->set_charset()?

Question

after setting all config file and runtime options for charset that i can find to utf-8, new mysqli connections made with php still has its charset set to latin1, which effective

Answer 1

You have diagnosed the basic problem correctly: While you can change the default MySQL client charset in the client machine's my.cnf or .my.cnf, these files are not used by PHP.

If you think about how PHP's MySQLi/MySQL extensions work, this will make sense -- they have nothing to do with the mysql client program and aren't going to crawl your filesystem for config files, because they use libmysql directly.

To change libmysql's actual default charset, you'll just need to rebuild libmysql. That may not be an answer you like (since you're using precompiled MySQL binaries), but it is the actual answer. The defaults are set at compile time, and then can be overridden at runtime.

If you don't want to do this and calling set_charset() annoys you, my suggestion would be to simply extend the MySQLi class and use that class in place of mysqli. i.e.:

class MyDB extends mysqli {
  // (You could set defaults for the params here if you want
  //  i.e. $host = 'myserver', $dbname = 'myappsdb' etc.)
  public function __construct($host = NULL, $username = NULL, $dbname = NULL, $port = NULL, $socket = NULL) {
    parent::__construct($host, $username, $dbname, $port, $socket);
    $this->set_charset("utf8");
  } 
} 

Typically in an application you'll have some kind of database abstraction layer anyway, so you can either have this layer use MyDB instead of mysqli, or you can have this layer be MyDB and add or override any methods you want (I've done this with simple ORM-less apps).

It's a good practice to always have some kind of database abstraction layer, even if it starts as just class MyDB extends mysqli {} because then you'll never have to search/replace your entire codebase to make small changes.

RE: your workaround, as you explain, this essentially hardcodes your entire db server to UTF-8 regardless of what clients request. Instead of having multiple databases, each with its own charset, the server only works with UTF-8 and may silently mangle data if clients connect with another charset. This is fundamentally wrong because you've effectively moved one aspect of your application's configuration (database charset) from the app/client machine to the database server where it doesn't really belong.

If you think about the application stack's layers,

[server] <=> [network] <=> [client libmysql] <=> [PHP binary] <=> [app]

then you'll understand that the "correct" place for an app-specific configuration like this is in the app itself, not elsewhere in the stack. You may not like having to specify your database's charset in PHP, but if you think about it, that's really where it belongs, because it's also where you're specifying the database itself that you want to connect to -- it's a connection parameter, not a server configuration issue. Hardcoding the charset anywhere else makes your application non-portable.