Connessioni multiple a mysql attraverso classe

[fai1881]

Ciao,

ho creato una classe di supporto per gestier le connessioni a mysql ma quando creo istanze multiple l'unica connessione che rimane attiva è l'ultima, qualcuno sa spiegarmi il perchè? (PHP 5.3)
Di seguito il codidce che mi stampa solo le tabelle dell'ultima connessione creata.....

class EntityManager {
    public $host;
    public $schemaName;
    public $username;
    public $password;
    public $persistent;
    
    public $connection;
    
    public function __construct($host, $schema, $username, $password, $persistent = false) {
        $this->host = $host;
        $this->schemaName = $schema;
        $this->username = $username;
        $this->password = $password;
        $this->persistent = $persistent;
    
        if ($this->persistent){
            $this->connection = mysql_pconnect( $this->host, $this->username, $this->password );
            if ( !mysql_ping( $this->connection ) ){
               $this->connection = mysql_pconnect( $this->host, $this->username, $this->password );
            }
        } else {
            $this->connection = mysql_connect( $this->host, $this->username, $this->password );
        }

        mysql_set_charset('utf8',$this->connection);

        if (!$this->connection) {
            die('Could not connect: ' . mysql_error($this->connection));
        }

        if (!mysql_select_db($this->schemaName, $this->connection)) {
            die("Unable to select mydbname: " . mysql_error($this->connection));
        }
    }
    
    public function close(){
        mysql_close($this->connection);
    }
    
    public function selectTables(){
        $result = $this->execQuery("SHOW TABLES");
        while($table = mysql_fetch_array($result)){
            echo $table[0].'
';
        }
        mysql_free_result($result);
    }

     ....
}

$emTest = new EntityManager($db_host, $test_db_name, $test_db_user, $test_db_password);
        $emPro = new EntityManager($db_host, $db_schema, $db_user_name, $db_password);
        
$emTest->selectTables();
$emPro->selectTables();