无法使用PDO连接到Oracle

I have these snippets but I still cannot connect to my Oracle DB. I believe I did everything right but i don't know where the pitfall is.

try {
    $user='weltesadmin'; // Enter your DB User Name.
    $pass='weltespass'; // Enter your DB Password.
    $dataBaseName='weltes'; // Enter your Database Name.
    $dbh = new PDO('OCI:dbname='.$dataBaseName.'charset=UTF-8', $user,$pass);
    echo "Connection Successful";
} catch (PDOException $e) {
    print "Error!: " . $e->getMessage() . " ";
    die();
}

And on the php.ini:

extension=php_openssl.dll
;extension=php_pdo_firebird.dll
extension=php_pdo_mysql.dll
extension=php_pdo_oci.dll
;extension=php_pdo_odbc.dll
;extension=php_pdo_pgsql.dll
extension=php_pdo_sqlite.dll
;extension=php_pdo_sqlite_external.dll
;extension=php_pgsql.dll
;extension=php_pspell.dll
;extension=php_shmop.dll

Check your installed drivers and see if oci is installed:

foreach(PDO::getAvailableDrivers() as $driver)
    echo $driver, '
';

If oci don't shown, then need to install it (http://php.net/manual/en/ref.pdo-oci.php)

My problem solved by following instructions on http://lacot.org/blog/2009/11/03/ubuntu-php5-oci8-and-pdo_oci-the-perfect-install.html

Do not forget to export oracle home .Even though oracle home was set i was not able to configure pdo_oci. So give export ORACLE_HOME=/opt/instantclient_10_2/ before running configure in pdo_oci-1.0 directory

1. enabling the above extensions

2. adding this to requirements.php

   array(
               'name' => 'PDO Oracle extension',
               'mandatory' => false,
               'condition' => extension_loaded('pdo_oci'),
               'by' => 'All DB-related classes',
               'memo' => 'Required for Oracle database.',
   ),
   

3. editing dsn in db.php as follows

   return [
           'class' => 'yii\db\Connection',
           'dsn'=> 'oci:dbname=(DESCRIPTION=(ADDRESS=(HOST=x.y.z.a)(PROTOCOL=tcp)(PORT=1525))(CONNECT_DATA=(SID=YOURSID)))',
           'username' => 'USER',
           'password' => 'PASS',
           'charset' => 'utf8',
   ];
   

Looking at the line:
$dbh = new PDO('OCI:dbname='.$dataBaseName.'charset=UTF-8', $user,$pass);
You have used OCI in caps replace that with "oci" (small case)
(A mistake I had made myself)
Once you change that uncommenting below line from php.ini is sufficient:
extension=php_pdo_oci.dll