从 PHP 连接到 Oracle 数据库

我有一个Oracle数据库，我正在尝试连接到它。

出于某种原因，当我尝试以下代码时：

<?php
    include "header.php";
    // simply attempt to connect to the database
    /* If you are connecting to the Oracle database, the credentials are as follows: 
     * Username: ********
     * Password: ********
     * Hostname: **********
     * Port: 1521
     * Service name: ***********
    */
    $oracleConnect = true;
    if ($oracleConnect)
    {
        echo 'Attempting connection...<br>';
        $connection = null;
        try
        {
            $connection = oci_connect('user',
                'pass',
                'user@//hostname:1521/dbname');
        }
        catch (Exception $e)
        {
            echo $e->getMessage();
        }
        if (!$connection)
        {
            echo '<p>Something is wrong.</p>';
            $e = oci_error();
            trigger_error(htmlentities($e['message'], ENT_QUOTES), E_USER_ERROR);
        }
        // if the connection has been established
        else
        {
            // tell the user and close it (this is a test)
            echo 'Connection established!!';
            oci_close($connection);
        }
    }
    else
    {
        $connection = new mysqli('host', 'user', 'password', 'database');
        echo ($connection) ? 'Database connection successful!' : 'Could not connect.';
    }
    include "footer.php";
?>

当我尝试上面的代码时，我得到"正在尝试连接..."打印，但没有别的。无论如何，它应该打印其他东西。可能出现什么问题？