title: ORACLE - ORA-01843: not a valid month
body: <p>I change OCI8 version for PHP and since this query dosn't work :</p>
  
  <pre><code>SELECT 'M'||to_char(to_date(OD.DATE2,'DD/MM/YYYY'),'MM') PERIODE, count(*) DATA, OD.DCCPT DCCPT
  FROM BDD OD
  WHERE BDD = 'phone'
  AND OD.SENS = 'Ent'
  AND OD.DCCPT IN('PIOLUC')
  AND (OD.DATE2 BETWEEN '08/03/2015' AND '08/03/2016')
  group by 'M'||to_char(to_date(OD.DATE2,'DD/MM/YYYY'),'MM'), OD.CDCCPT CDCCPT
  </code></pre>
  
  <p>I got this message :</p>
  
  <p><strong>Message:  oci_execute(): ORA-01843: not a valid month</strong></p>
  
  <p>It works with Toad for Oracle 11. Do you have any solution ?</p>
  
  <p>Thank you :)</p>