MySQLi预处理语句中的绑定参数

Question

sample1:

<?php
  $mysqli = new mysqli("localhost","root","","test");

  /*check connection*/
  if(mysqli_connect_errno())
  {
    printf("connection failed: %s
",mysqli_connect_error());
    exit();
  }

  /*create prapared statement*/

  $stmt1 = $mysqli->prepare("select id from posts");
  $stmt2 =$mysqli->prepare("select username from members where id=?"); 

  test($stmt1,$stmt2);//function call  

  function test($stmt1,$stmt2)
  {
   $stmt1->execute(); 

   $stmt1->store_result();

   $stmt1->bind_result($ID);

   while($stmt1->fetch())
   {
      **/*bind params*/
      $stmt2->bind_param('i',$id); /*HERE,BINDING MANY TIMES*/**

      /*set params*/
      $id =$ID;

      /*execute prapared statement*/
      $stmt2->execute();

      /*bind results*/
      $stmt2->bind_result($username);

      while($stmt2->fetch())
      {
        echo 'Username: '.$username.'<br/>';
      }     

   }     

  }


?>    

sample2:

<?php
  $mysqli = new mysqli("localhost","root","","test");

  /*check connection*/
  if(mysqli_connect_errno())
  {
    printf("connection failed: %s
",mysqli_connect_error());
    exit();
  }

  /*create prapared statement*/

  $stmt1 = $mysqli->prepare("select id from posts");
  $stmt2 =$mysqli->prepare("select username from members where id=?"); 

  test($stmt1,$stmt2);//function call  

  function test($stmt1,$stmt2)
  {
   $stmt1->execute(); 

   $stmt1->store_result();

   $stmt1->bind_result($ID);

   **/*bind params*/
    $stmt2->bind_param('i',$id); /*HERE,BINDING ONCE*/**

   while($stmt1->fetch())
   {       

      /*set params*/
      $id =$ID;

      /*execute prapared statement*/
      $stmt2->execute();

      /*bind results*/
      $stmt2->bind_result($username);

      while($stmt2->fetch())
      {
        echo 'Username: '.$username.'<br/>';
      }     

   }     

  }


?>    

Is there any performance difference in both the ways how parameters are bound (shown in bold in sample1 and sample2) or MySQLi automatically handles this? In sample1,although it is unnecessary bind_param is included inside the while loop.

Answer 1

Calling a function repeatedly is more expensive than not calling it repeatedly, so there should be a small performance gain in the second version. There's no point in calling bind_param inside the loop since it's unnecessary -- the first call binds to a reference to the variable, so all you have to do is reassign the variable.