如果绑定参数返回错误，则重定向

Question

I am trying to have my page redirect to another script which will display all error messages if there should be any. Here is what I am trying to do:

//Prepare statement    
$checkCode = $conn->prepare("SELECT COUNT(code) FROM subscribers WHERE code LIKE ?");

    if(!$checkCode){
         header('Location:'.$errorURL."?&notification=prepareFailed");
         die();
    }else{
         $checkCode->bind_param("s", $code);
              if(!$checkcode){
                   header('Location:'.$errorURL."?&notification=bindParamFailed");
                   die();
              }else{
                   $checkCode->execute();
                   if(!$checkCode){
                        header('Location:'.$errorURL."?&notification=executeFailed");
                        die();
                   else{
                        //store result in a variable etc.}
     }

$conn and $errorURL are obviously declared. $code is previously retrieved from the database.

This code redirects me to the page whose URL ends in bindParamFailed, therefore the error comes from the bind_param statement. If I comment out the if(!$checkCode){...} part it work like a charm.

Why is it not working? Any ideas?

Are there any other (maybe more intelligent) ways of programming such a custom error page?

Answer 1

While the $conn->prepare() statement will return boolean false into the variable $checkCode on failure, the other calls you are making on the $checkCode object will not modify the object. It will still be "truthy", so if ($checkCode) isn't meaningful and the error states will never be entered, even if the bind/execute code fails.

Instead you need to check the values returned by those method calls for success or failure instead of checking if ($checkCode) again. I'd recommend refactoring it into a chain of if(), each of which has the potential to redirect away.

//Prepare statement    
// If this fails, $checkCode will indeed be boolean false
$checkCode = $conn->prepare("SELECT COUNT(code) FROM subscribers WHERE code LIKE ?");

if(!$checkCode){
  header('Location:'.$errorURL."?&notification=prepareFailed");
  die();
}

// No need for the else because you cannot reach this code unless the previous
// block was true -- it would redirect away on error.
if (!$checkCode->bind_param("s", $code)) {
  header('Location:'.$errorURL."?&notification=bindParamFailed");
  die();
}

// Same here...
if (!$checkCode->execute()) {
  header('Location:'.$errorURL."?&notification=executeFailed");
  die();
}

// All is well, store the variable
// and perform the rest of your code...

This could be refactored a little more to call header() only once and set an error string on the prior errors.

//Prepare statement    
$checkCode = $conn->prepare("SELECT COUNT(code) FROM subscribers WHERE code LIKE ?");

if(!$checkCode){
  $err = "prepareFailed";
}
// On subsequent checks, test that the $err variable is still empty
// If it isn't, that section will be skipped and you'll fall through to the
// redirection header() call.
if (empty($err)) {
  if (!$checkCode->bind_param("s", $code)) {
    $err = "bindParamFailed";
  }
}
if (empty($err)) {
  if (!$checkCode->execute()) {
    $err = "executeFailed";
  }
}

// Now, if the $err string is non-empty, redirect with the message
if (!empty($err)) {
  header('Location:'.$errorURL."?&notification=$err");
  die();
}
else {
  // All is well, store the variable
  // and perform the rest of your code...
}