如果在PDO预处理语句中插入成功，则为if / else语句的语法

Question

I'm trying to switch from mySql statements to PDO prepared statements, but I'm having trouble figuring out the correct syntax for the if/else statements that I have to use if the insert was successful (which were previously if($result) {...}).

I know that $stmt->execute(); returns true on success or false on failure, but I haven't been able to determine how to set the statement up to act on that.

The new code (PDO prepared statement)

$gender = $_POST['gender'];  
if ($gender==="female" ) {
try {      
   $stmt = $conn->prepare('INSERT INTO customer_info (fname...) VALUES(:fname...)');
   $stmt->bindParam(':fname', $_POST['fname'], PDO::PARAM_STR);
   $stmt->execute();   
    } catch(PDOException $e) {
  echo $e->getMessage();
}

This is the rest of the original if ($gender==="female") function

$result = @mysql_query($qry);    
    if($result) {          
      $qry="SELECT * FROM customer_info WHERE user_name='$_POST['user_name']' AND password='$_POST['password']'";
      $result=mysql_query($qry);          
if($result) {
    if(mysql_num_rows($result) == 1) {
        //user_name Successful
        session_regenerate_id();
        $member = mysql_fetch_assoc($result);
        $_SESSION['SESS_USER_ID'] = $member['user_id'];
        session_write_close();
        header("location: flatter_iframe.html");
        exit();
    }else {        
        header("location: login_failed.html");
        exit();
    }   

I've deleted most of the variables in order to simplify things (since the code is the same)

Answer 1

There are a number of ways you can check whether an INSERT worked correctly.

1. Return value from $stmt->execute()

As you said, $stmt->execute(); returns true on success or false on failure. So you can use:

$result = $stmt->execute();
if ($result) {...}

PDO Execute documentation here

2. Row Count

rowCount will return the number of rows afffected by a query. After a successful insert, this should be 1.

$stmt->execute();
$affected_rows = $stmt->rowCount();
if ($affected_rows == 1) {...} 

PDO rowCount documentation here

3. Last Inserted Id

If your table has an ID column, you can return the ID of the last inserted row using lastInsertId().

$stmt->execute();
$newCustomerInfoId = $pdo->lastInsertId();
if ($newCustomerInfoId) {...}

Note: You must call lastInsertId on the PDO object, not the $stmt.

PDO lastInsertId documentation here