Each insert must be successful - define what you mean by successful:
- whether the record was inserted or
- whether it already exists and did not need the insert or
- that the insert values were not acceptable for other reasons like field type and size checks.

Similarly about the definition of the UPDATE sql being successful:
- was the update successful in general
- was the update unnecessary as the record was already in the updated state
- was the update not acceptable at all for reasons like field type and size check failure.

function autocommitfalse(){
      global $db;
      /* switch autocommit status to FALSE. Actually, it starts transaction */
      return mysqli_autocommit($db, FALSE);
}

function autocommittrue(){
      global $db;
      return mysqli_autocommit($db, TRUE);
}

function commitquery(){
     global $db;
     return mysqli_commit($db);
}

function rollbackedquery(){
     global $db;
     return mysqli_rollback($db);
}

======

try {
    
     autocommitfalse();

    $SQLSELECT = "SELECT * FROM BC ";
    $result_as = db_query($SQLSELECT);

    if(!$result_as ){
            throw new Exception('Wrong SQL SELECT: ' . $SQLSELECT_a. ' Error: '.db_error_msg($db) . db_error_no());
     }
 

    $sqla ="INSERT INTO A () VALUES () ";
    $result_a = db_query($sqla);

    if(!$result_a){
            throw new Exception('Wrong SQL SELECT: ' . $result_a. ' Error: '.db_error_msg($db) . db_error_no());
     }
 
   
    $sqlb ="INSERT INTO B () VALUES () ";
    $result_b =db_query($sqlb);
   
    if(!$result_b){
            throw new Exception('Wrong SQL SELECT: ' . $result_a. ' Error: '.db_error_msg($db) . db_error_no());
     }
  
    $sqlCb ="UPDATE CB ()  SET ...   ";
    $result_Cb =db_query($sqlCb);

    if($result_Cb === false  &&  mysqli_affected_rows($db) == 0 ){
            throw new Exception('Wrong SQL SELECT: ' . $result_a. ' Error: '.db_error_msg($db) . db_error_no());
     }
     

    commitquery();
    echo 'Transaction completed successfully!';

} catch (Exception $e) {

        echo"<br \>";
        echo "<table align=center><tr><td>";
        echo $e->getMessage();
        echo "</td></tr></table>";
        echo"<br \>";

        echo display_error(_("Transaction failed: transaction rolled back"));
        rollbackedquery();
   }        

        autocommittrue();

If something wrong ..please let me know with change in it ( above code ) ..so that i am more clear ....

Ohh i think still not rollback... hmm admin please help me guys please

Can you modify above code and let me know what exact you mean to say , as i got to know that :

mysql_affected_rows() should be more useful to return true update and insert.

Please help me with above example in your way. so that i would be more clear what you want to say.

http://stackoverflow.com/questions/14908087/should-mysqli-update-queries-return-a-result
http://stackoverflow.com/questions/12990164/how-to-check-if-an-update-mysqli-query-is-correctly-executed
http://stackoverflow.com/questions/12744953/mysqli-returns-true-for-insert-query-row-not-inserted

UPDATE will return 0 rows affected if the changed state already exists and the mysql_query function will still return true. Hence remove the UPDATE check in the if statement.

$result_a = db_query($sqla);
$result_b = db_query($sqlb);
$result_Cb = db_query($sqlCb);

if ( $result_a && $result_b && $result_Cb ) {
                db_query("COMMIT");
                echo display_notification_centered(_("Database transaction was successful."));
            } else {       
                db_query("ROLLBACK");
               echo display_notification_centered(_("transaction rolled back"));
                exit;
            }

Try {} Catch {} Transaction for FA ?

I am using currently as :

db_query("START TRANSACTION");

$sqla ="INSERT INTO A () VALUES () ";
db_query($sqla);

$sqlb ="INSERT INTO B () VALUES () ";
db_query($sqlb);

$sqlCb ="UPDATE CB ()  SET ...   ";
db_query($sqlCb);

if ( $sqla and $sqlb and $sqlCb ) {
                db_query("COMMIT");
                echo display_notification_centered(_("Database transaction was successful."));
            } else {        
                db_query("ROLLBACK");
               echo display_notification_centered(_("transaction rolled back"));
                exit;
            }

I am Right ? ...

Can any one please tell me same in TRY .. CATCH ? ....