PHP Oracle Warnings

I'm getting PHP Warnings that I'm not able to debug and can't find any useful explanations when searching:

$sql = "select PRODUCT from table where ... ";
            
      $rs = oci_parse($this->Connection,$sql);
      oci_execute($rs);

      if($row = oci_fetch_object($rs, OCI_ASSOC)) {
            $myobjects->product = $row->PRODUCT;
      }
      
PHP Warning:  oci_execute(): ORA-00936: missing expression
PHP Warning:  oci_fetch_object(): ORA-24374: define not done before fetch or execute and fetch in ...

Any assistance would be appreciated!