getting message: oci_execute(): ORA-00942: table or view does not exist

hi all, 
still getting same error , please help, i will be much grateful  
regards

EDIT: have attached 4 files
1) database.php
2) controller/Depts.php
3) model/Dep_models.php
4) views/Dep_view.php

database.php have been modified for 'oracle' (referred to a solution while searching for)
as mentioned earlier: Database is Oracle 12c Release 2
unremark in apache/bin/php.ini following lines:

extension=pdo_oci
extension=oci8_12c  ; Use with Oracle Database 12c Instant Client

found somewhere and created new php file and it runs, showing data from table.column used in Select statement: ( i know its not CI but PHP ) 

PHP Code:

<?php
$c = oci_connect('hr', 'hr', 'localhost/orclpdb');
$s = oci_parse($c, 'select city from locations');
oci_execute($s);
while (($res = oci_fetch_array($s, OCI_ASSOC)) != false) {
 echo htmlentities($res['CITY']) . "<br>";
}
?>

Attached Files

  database.php (Size: 5.33 KB / Downloads: 47)
  Depts.php (Size: 1.74 KB / Downloads: 45)
  Dep_models.php (Size: 1.53 KB / Downloads: 42)
  Dep_view.php (Size: 1.92 KB / Downloads: 15)