oci_fetch_array返回false

$sql = 'SELECT * FROM reunion';
$stmt = oci_parse($conn, $sql);

oci_execute($stmt);

echo '<pre>';

echo 'Reached'; // works

while (($row = oci_fetch_array($stmt, OCI_BOTH)) != false) {
   print_r($row);  // prints nothing 
}

echo '</pre>';
oci_commit($conn);
oci_close($conn);

The above code prints nothing ! I have tested the connection and the table contains rows.

According to the official docs, oci_fetch_array returns an array containing the next result-set row of a query. Each array entry corresponds to a column of the row. This function is typically called in a loop until it returns FALSE, indicating no more rows exist.