PHP, MySQL & encoding detection

$db_handle = mysql_connect('localhost', 'username', 'password');
mysql_select_db('my_db');

mysql_set_charset('utf8', $db_handle);

// ------ INSERT: First example -------
$s        = "je viens de télécharger et installer le logiciel";
$encoding = mb_detect_encoding($s, 'ASCII,UTF-8,ISO-8859-15', true);
if ($encoding != 'UTF-8') { $s = iconv($encoding, 'UTF-8', $s); }

mysql_query("INSERT INTO my_table (post_id, post_subject, post_text) VALUES (1, 'subject 1', '$s')", $db_handle);

// ------ INSERT: Second example -------
$s        = "EPrints and العربية";
$encoding = mb_detect_encoding($s, 'ASCII,UTF-8,ISO-8859-15', true);
if ($encoding != 'UTF-8') { $s = iconv($encoding, 'UTF-8', $s); }
mysql_query("INSERT INTO my_table (post_id, post_subject, post_text) VALUES (2, 'subject 2', '$s')", $db_handle);
// -------------

mysql_close($db_handle);