mysqli::prepare

mysqli_prepare

(PHP 5, PHP 7, PHP 8)

mysqli::prepare -- mysqli_prepare — 准备执行一个 SQL 语句

说明

面向对象风格

mysqli::prepare ( string $query ) : mysqli_stmt

过程化风格

mysqli_prepare ( mysqli $link , string $query ) : mysqli_stmt

做好执行 SQL 语句的准备，返回一个语句句柄，可以对这个句柄进行后续的操作。 这里仅仅支持单一的 SQL 语句，不支持多 SQL 语句。

在执行语句之前，需要使用 mysqli_stmt_bind_param() 函数 对占位符参数进行绑定。 同样，在获取结果之前，必须使用 mysqli_stmt_bind_result() 函数对返回的列值进行绑定。

参数

link

仅以过程化样式：由mysqli_connect() 或 mysqli_init() 返回的链接标识。

query

SQL 语句。

Note:

不需要在语句末尾增加分号（;） 或者 \g 结束符。

SQL 语句中可以包含一个或者多个问号（?） 表示语句的参数。

Note:

SQL 语句中，仅允许在特定的位置出现问号参数占位符。 例如，在 INSERT 语句中的 VALUES() 子句中可以使用参数占位符，来表示对应列的值。 也可以在 WHERE 字句中使用参数来表示 要进行比较的值。

但是，并不是所有的地方都允许使用参数占位符， 例如对于表名、列名这样的 SQL 语句中的标识位置， 就不可以使用参数占位。 SELECT 语句中的列名就不可以使用参数。 另外，对于 = 这样的逻辑比较操作也不可以在两侧都使用参数， 否则服务器在解析 SQL 的时候就不知道该如何检测参数类型了。 也不可以在 NULL 条件中使用问号， 也就是说不可以写成：? IS NULL。 一般而言，参数也只能用在数据操作（DML）语句中， 不可以用在数据定义（DDL）语句中。

返回值

mysqli_prepare() 返回一个 statement 对象，如果发生错误则返回 false。

范例

Example #1 mysqli::prepare() 例程

面向对象风格

<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");

/* 检查连接 */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}

$city = "Amersfoort";

/* 创建一个预编译 SQL 语句 */
if ($stmt = $mysqli->prepare("SELECT District FROM City WHERE Name=?")) {

    /* 对于参数占位符进行参数值绑定 */
    $stmt->bind_param("s", $city);

    /* 执行查询 */
    $stmt->execute();

    /* 将查询结果绑定到变量 */
    $stmt->bind_result($district);

    /* 获取查询结果值 */
    $stmt->fetch();

    printf("%s is in district %s\n", $city, $district);

    /* 关于语句对象 */
    $stmt->close();
}

/* 关闭连接 */
$mysqli->close();
?>

过程化风格

<?php
$link = mysqli_connect("localhost", "my_user", "my_password", "world");

/* 检查连接 */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}

$city = "Amersfoort";

/* 创建一个预编译 SQL 语句 */
if ($stmt = mysqli_prepare($link, "SELECT District FROM City WHERE Name=?")) {

    /* 对于参数占位符进行参数值绑定 */
    mysqli_stmt_bind_param($stmt, "s", $city);

    /* 执行查询 */
    mysqli_stmt_execute($stmt);

    /* 将查询结果绑定到变量 */
    mysqli_stmt_bind_result($stmt, $district);

    /* 获取查询结果值 */
    mysqli_stmt_fetch($stmt);

    printf("%s is in district %s\n", $city, $district);

    /* 关闭语句句柄 */
    mysqli_stmt_close($stmt);
}

/* 关闭连接 */
mysqli_close($link);
?>

以上例程会输出：

Amersfoort is in district Utrecht

参见

User Contributed Notes

wapharshitsingh at gmail dot com 12-May-2021 03:41
just wanted to share here, how we can use prepare statement with the combination of ... operator effectively .
<?php
class Database{
 private function getTypeofValues($string, $value){
        if(is_float($value)){
            $string .= "d";
        }elseif(is_integer($value)){
            $string .= "i";
        }elseif(is_string($value)){
            $string .= "s";
        }else{
            $string .= "b";
        }
        return $string;
    }
 public function makeQuery($query, array $values){
        $stmt = $this->connection->prepare($query);
        $type = array_reduce($values, array($this, "getTypeOfValues"));
        $stmt->bind_param($type, ...$values);
        $stmt->execute();
        $result = $stmt->get_result();
        return $result;
    }
}
?>
omidbahrami1990 at gmail dot com 06-Dec-2017 10:49
This Is A Secure Way To Use mysqli::prepare
--------------------------------------------------------
<?php
function secured_signup($username,$password)
{   
$connection = new mysqli($dbhost,$dbusername,$dbpassword,$dbname);   
if ($connection->connect_error)
die("Secured");
   
$prepared = $connection->prepare("INSERT INTO `users` ( `username` , `password`  ) VALUES ( ? , ? ) ; ");
if($prepared==false)
die("Secured");
   
$result=$prepared->bind_param("ss",$username,$password);
if($result==false)
die("Secured");
   
$result=$prepared->execute();   
if($result==false)
die("Secured");
       
$prepared->close();
$connection->close();   
}
/*
$dbhost ---> DataBase IP Address
$dbusername ---> DataBase Username
$dbpassword ---> DataBase Password
$dbname ---> DataBase Name
*/
?>
kritz at hrz dot tu-chemnitz dot de 10-May-2017 08:57
I wasn't able to fully test the following since the server I am currently working on is missing the PHP module that allows me to call get_result on mysqli_stmt but maybe this could be helpful for someone:

<?php

/**
 * Custom {@link \mysqli} class with additional functions.
 */
class CustomMysqli extends \mysqli
{
    /**
     * Creates a prepared query, binds the given parameters and returns the result of the executed
     * {@link \mysqli_stmt}.
     * @param string $query
     * @param array $args
     * @return bool|\mysqli_result
     */
    public function queryPrepared($query, array $args)
    {
        $stmt   = $this->prepare($query);
        $params = [];
        $types  = array_reduce($args, function ($string, &$arg) use (&$params) {
            $params[] = &$arg;
            if (is_float($arg))         $string .= 'd';
            elseif (is_integer($arg))   $string .= 'i';
            elseif (is_string($arg))    $string .= 's';
            else                        $string .= 'b';
            return $string;
        }, '');
        array_unshift($params, $types);

        call_user_func_array([$stmt, 'bind_param'], $params);

        $result = $stmt->execute() ? $stmt->get_result() : false;

        $stmt->close();

        return $result;
    }
}

$db = new CustomMysqli('host', 'user', 'password', 'database', 3306);
$result = $db->queryPrepared(
    'SELECT * FROM table WHERE something = ? AND someotherthing = ? AND elsewhat = ?',
    [
        'dunno',
        1,
        'dontcare'
    ]
);

if (isset($result) && $result instanceof \mysqli_result) {
    while (null !== ($row = $result->fetch_assoc())) {
        echo '<pre>'.var_debug($row, true).'</pre>';
    }
}

?>

NOTE: If you want to use this with a PHP version below 5.4 you have to use the old ugly array() syntax for arrays instead of the short [] syntax.
cdtreeks at gmail dot com 11-Jan-2015 01:23
When executing a prepared MySQL, by default if there's an error then you'll simply get FALSE returned from your call to prepare().

To get the full MySQL error back create a statement object before preparing your query as such:

<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");

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

$city = "Amersfoort";

/* create a prepared statement */
$statement = $mysqli->stmt_init();
if ($statement->prepare("SELECT District FROM City WHERE Name=?")) {

    /* bind parameters for marker(s) */
    $statement->bind_param("s", $city);

    /* execute query */
    if (!$statement->execute()) {
        trigger_error('Error executing MySQL query: ' . $statement->error);
    }

    /* bind result variables */
    $statement->bind_result($district);

    /* fetch value */
    $statement->fetch();

    printf("%s is in district %s\n", $city, $district);

    /* close statement */
    $statement->close();
}

/* close connection */
$mysqli->close();
?>
REz 05-Nov-2014 11:35
There is no reference that all data must be fetched before a new prepare call to msqli, the only help is in a 6 years old comment!
You have to myslqi_stmt::fetch() data until NULL is returned before you can call mysqli::prepare() again without having FALSE and no error at all in mysqli::$errno and mysqli::$error
marmstro at gmail dot com 04-Oct-2013 03:05
If your IDE isn't recognizing $stmt as an object of type mysqli_stmt when you use the traditional perpare:

$stmt = mysqli_prepare($link, $query);

The following works and is IDE friendly:

$stmt = new mysqli_stmt($link, $query);
@runspired 31-Jan-2013 04:42
I don't think this is a bug, just an unexpected behavior.  While building an API I discovered that passing INT 0 instead of STRING '0' into a prepared statement caused my script to run out of memory and produce a 500error on the webpage.

A simplified example of this issue is below: ($_DB is a global reference to a mysqli connection)

<?php
function getItem( $ID ) {

     $_STATEMENT = $_DB->prepare("SELECT item_user, item_name, item_description FROM item WHERE item_id = ?;");

     $_STATEMENT->bind_param( 'i' , $ID );

     $_STATEMENT->execute();
     $_STATEMENT->store_result();

     $_STATEMENT->bind_result( $user , $name , $description);
     $result = $_STATEMENT->fetch();

     $_STATEMENT->free_result();
     $_STATEMENT->close();

     return $result;
}

getItem(0); //fails!
getItem('0'); //works!

?>

The best I can guess is that an INT 0 gets translated as BOOLEAN , and if this is indeed the case it should be documented above, but all efforts to get error information (via the php script) have failed.
timchampion dot NOSPAM at gmail dot com 17-Feb-2012 08:56
Just wanted to make sure that all were aware of get_result.

In the code sample, after execute(), perform a get_result() like this:

<?php

// ... document's example code:

    /* bind parameters for markers */
    $stmt->bind_param("s", $city);

    /* execute query */
    $stmt->execute();

    /* instead of bind_result: */
    $result = $stmt->get_result();

    /* now you can fetch the results into an array - NICE */
    while ($myrow = $result->fetch_assoc()) {

        // use your $myrow array as you would with any other fetch
        printf("%s is in district %s\n", $city, $myrow['district']);

    }
?>

This is much nicer when you have a dozen or more fields coming back from your query.  Hope this helps.
Bernie van&#39;t Hof 02-Feb-2012 06:38
Prepared statements are confusing in the beginning ..

mysqli->prepare() returns a so-called statement object which is used for subsequent operations eg execute, bind_param, store_result, bind_result, fetch, etc.

The statement object has private properties which update as each statement operation is carried out. I found these useful for understanding what is going on when writing a prepared statement function:

affected_rows
insert_id
num_rows
param_count
field_count
errno
error
sqlstate
id

But it took a little time to get my head around accessing them:

<?php
$stmt = $mysqli->prepare($query);

//       .. $stmt-> operations ..

var_dump($stmt); // shows null values

var_dump($stmt->errno); // note literal, displays value

//       .. $stmt-> operations ..

// to keep a copy ..
// get_object_properties() won't work
// clone() won't work
$properties = array();
foreach ($stmt as $name => $priv){
    $properties[$name] = $stmt->$name; //    works
    // $properties[$name] = $priv; //    won't work, foreach can't access private properties
}

$stmt->close();
// var_dump($stmt->errno) // won't work, $stmt is closed
?>
Darren 13-Jan-2012 11:09
I wrote this function for my personal use and figured I would share it.  I am not sure if this is the appropriate forum but I wish I had this when I stumbled on to mysqli::prepare.  The function is an update of the function I posted previously.  The previous function could not handle multiple queries.

For queries:
Results of single queries are given as arrays[row#][associated Data Array]
Results of multiple queries are given as arrays[query#][row#][associated Data Array]

For queries which return an affected row#, affected rows are returned instead of (array[row#][associated Data Array])

Code and example are below:

<?php
function mysqli_prepared_query($link,$sql,$typeDef = FALSE,$params = FALSE){
  if($stmt = mysqli_prepare($link,$sql)){
    if(count($params) == count($params,1)){
      $params = array($params);
      $multiQuery = FALSE;
    } else {
      $multiQuery = TRUE;
    } 
   
    if($typeDef){
      $bindParams = array();   
      $bindParamsReferences = array();
      $bindParams = array_pad($bindParams,(count($params,1)-count($params))/count($params),"");        
      foreach($bindParams as $key => $value){
        $bindParamsReferences[$key] = &$bindParams[$key]; 
      }
      array_unshift($bindParamsReferences,$typeDef);
      $bindParamsMethod = new ReflectionMethod('mysqli_stmt', 'bind_param');
      $bindParamsMethod->invokeArgs($stmt,$bindParamsReferences);
    }
   
    $result = array();
    foreach($params as $queryKey => $query){
      foreach($bindParams as $paramKey => $value){
        $bindParams[$paramKey] = $query[$paramKey];
      }
      $queryResult = array();
      if(mysqli_stmt_execute($stmt)){
        $resultMetaData = mysqli_stmt_result_metadata($stmt);
        if($resultMetaData){                                                                              
          $stmtRow = array();  
          $rowReferences = array();
          while ($field = mysqli_fetch_field($resultMetaData)) {
            $rowReferences[] = &$stmtRow[$field->name];
          }                               
          mysqli_free_result($resultMetaData);
          $bindResultMethod = new ReflectionMethod('mysqli_stmt', 'bind_result');
          $bindResultMethod->invokeArgs($stmt, $rowReferences);
          while(mysqli_stmt_fetch($stmt)){
            $row = array();
            foreach($stmtRow as $key => $value){
              $row[$key] = $value;          
            }
            $queryResult[] = $row;
          }
          mysqli_stmt_free_result($stmt);
        } else {
          $queryResult[] = mysqli_stmt_affected_rows($stmt);
        }
      } else {
        $queryResult[] = FALSE;
      }
      $result[$queryKey] = $queryResult;
    }
    mysqli_stmt_close($stmt);  
  } else {
    $result = FALSE;
  }
 
  if($multiQuery){
    return $result;
  } else {
    return $result[0];
  }
}
?>

Example(s):
For a table of firstName and lastName:
John Smith
Mark Smith
Jack Johnson
Bob Johnson

<?php
//single query, single result
$query = "SELECT * FROM names WHERE firstName=? AND lastName=?";
$params = array("Bob","Johnson");

mysqli_prepared_query($link,$query,"ss",$params)
/*
returns array(
0=> array('firstName' => 'Bob', 'lastName' => 'Johnson')
)
*/

//single query, multiple results
$query = "SELECT * FROM names WHERE lastName=?";
$params = array("Smith");

mysqli_prepared_query($link,$query,"s",$params)
/*
returns array(
0=> array('firstName' => 'John', 'lastName' => 'Smith')
1=> array('firstName' => 'Mark', 'lastName' => 'Smith')
)
*/

//multiple query, multiple results
$query = "SELECT * FROM names WHERE lastName=?";
$params = array(array("Smith"),array("Johnson"));

mysqli_prepared_query($link,$query,"s",$params)
/*
returns array(
0=>
array(
0=> array('firstName' => 'John', 'lastName' => 'Smith')
1=> array('firstName' => 'Mark', 'lastName' => 'Smith')
)
1=>
array(
0=> array('firstName' => 'Jack', 'lastName' => 'Johnson')
1=> array('firstName' => 'Bob', 'lastName' => 'Johnson')
)
)
*/
?>

Hope it helps =)
Darren 11-Jan-2012 03:59
For those learning mysqli::prepare and mysqli_stmt::bind_params for the first time, here is a commented block of code which executes prepared queries and returns data in a similar format to the return values of mysqli_query.  I tried to minimize unnecessary classes, objects, or overhead for two reasons:
1) facilitate learning
2) allow relativity interchangeable use with mysqli_query

My goal is to lower the learning curve for whoever is starting out with these family of functions.  I am by no means an expert coder/scripter, so I am sure there are improvements and perhaps a few bugs, but I hope not =)

<?php
/*
Function: mysqli_prepared_query()
  Executes prepared querys given query syntax, and bind parameters
  Returns data in array format

Arguments:
  mysqli_link
  mysqli_prepare query
  mysqli_stmt_bind_param argmuent list in the form array($typeDefinitinonString, $var1 [, mixed $... ])

Return values:
  When given SELECT, SHOW, DESCRIBE or EXPLAIN statements: returns table data in the form resultArray[row number][associated field name]
  Returns number of rows affacted when given other queries
  Returns FALSE on error                       
*/
function mysqli_prepared_query($link,$sql,$bindParams = FALSE){
  if($stmt = mysqli_prepare($link,$sql)){
    if ($bindParams){                                                                                                   
      $bindParamsMethod = new ReflectionMethod('mysqli_stmt', 'bind_param');  //allows for call to mysqli_stmt->bind_param using variable argument list      
      $bindParamsReferences = array();  //will act as arguments list for mysqli_stmt->bind_param 
     
      $typeDefinitionString = array_shift($bindParams);
      foreach($bindParams as $key => $value){
        $bindParamsReferences[$key] = &$bindParams[$key]; 
      }
     
      array_unshift($bindParamsReferences,$typeDefinitionString); //returns typeDefinition as the first element of the string 
      $bindParamsMethod->invokeArgs($stmt,$bindParamsReferences); //calls mysqli_stmt->bind_param suing $bindParamsRereferences as the argument list
    }
    if(mysqli_stmt_execute($stmt)){
      $resultMetaData = mysqli_stmt_result_metadata($stmt);
      if($resultMetaData){                                                                              
        $stmtRow = array(); //this will be a result row returned from mysqli_stmt_fetch($stmt)  
        $rowReferences = array();  //this will reference $stmtRow and be passed to mysqli_bind_results
        while ($field = mysqli_fetch_field($resultMetaData)) {
          $rowReferences[] = &$stmtRow[$field->name];
        }                               
        mysqli_free_result($resultMetaData);
        $bindResultMethod = new ReflectionMethod('mysqli_stmt', 'bind_result');
        $bindResultMethod->invokeArgs($stmt, $rowReferences); //calls mysqli_stmt_bind_result($stmt,[$rowReferences]) using object-oriented style
        $result = array();
        while(mysqli_stmt_fetch($stmt)){
          foreach($stmtRow as $key => $value){  //variables must be assigned by value, so $result[] = $stmtRow does not work (not really sure why, something with referencing in $stmtRow)
            $row[$key] = $value;          
          }
          $result[] = $row;
        }
        mysqli_stmt_free_result($stmt);
      } else {
        $result = mysqli_stmt_affected_rows($stmt);
      }
      mysqli_stmt_close($stmt);
    } else {
      $result = FALSE;
    }
  } else {
    $result = FALSE;
  }
  return $result;
}

?>

Here's hoping the PHP gods don't smite me.
Zeebuck 24-Jul-2011 12:51
I think that the purpose that it was originally built for, and the purpose that people use it for today, have diverged.  But why dwell on the original purpose?  Obviously more code has been put into prepared statements today to allow it to be used to prevent sql injections, so it is now part of the design purpose today, as well as performance on repeatable statements.
Codeguy 29-Apr-2011 07:39
The actual purpose to use a prepared statement in sql is to cut the cost of processing queries; NOT to separate data from query. That's how it's being used w/ php NOW, not how it was designed to be used in the first place. With SQL you cut the cost of executing multiple similar queries down by using a prepared statement.. Doing so cuts out the parsing, validation and most often generates an execution plan for said query up front. Which is why they run faster in a loop, than their  IMMEDIATE Query cousins do. Do not assume that just because someone uses php and this function this way does not mean that it is THE way, or only way to do it. Although it is more secure than general queries but they are also more limited in what they can do or more precisely how you can go about doing it.
prwexler at earthlink dot net 09-Apr-2011 04:14
Actually, the purpose of a prepare statement is to separate user input from SQL commands.  This increases security by preventing a user from executing his own SQL code and damaging the integrity of a database.
sdepouw at NOSPAM dot com 29-Jul-2009 06:03
I don't know how obvious this was for anyone else, but if you attempt to prepare a query for a table that doesn't exist in the database the connection currently points to (or if your query is invalid in some other way, I suppose), an object will not be returned. I only noticed this after doing some digging when I kept getting a fatal error saying that my statement variable was not an set to an instance of an object (it was probably null).

Replace NOSPAM with nimblepros to e-mail me.
rafael at stiod dot com 29-Sep-2008 04:44
All data must be fetched before a new statement prepare
admin at xorath dot com 15-Aug-2007 10:39
Performance note to those who wonder. I performed a test where first of all inserted about 30,000 posts with one PK:id and a varchar(20), where the varchar data was md5-hash for the current iterator value just to fill with some data.

The test was performed on a dedicated ubuntu 7.04 server with apache2/php5/mysql5.0 running on Athlon 64 - 3000+ with 512MB of RAM. The queries where tested with a for-loop from 0 to 30000 first with:

<?php
for ( $i = 0; $i <= 30000; ++$i )
{
    $result = $mysqli->query("SELECT * FROM test WHERE id = $i");
    $row = $result->fetch_row();
    echo $row[0]; //prints id
}
?>

which gave a page-load time of about 3.3seconds avarage, then with this loop:

<?php
$stmt = $mysqli->prepare("SELECT * FROM test WHERE id = ?");
for ( $i = 0; $i <= 30000; ++$i )
{
    $stmt->bind_param("i", $i);
    $stmt->execute();
    $stmt->bind_result($id, $md5);
    $stmt->fetch();
    echo $id;
}
$stmt->close();
?>

and the avarage page-load was lowered by 1.3sec, which means about 2.0 sec avarage! Guess the performance difference could be even greater on a more complex/larger table and more complex SQL-queries.
nom0ny at yahoo dot com 25-May-2007 12:30
It must be noted in the Description whether developers should call mysqli_stmt_close prior to executing mysqli_prepare again on the same statement variable.

Example, Script A calls mysqli_stmt_close twice:
<?php
/* Script A -- We are already connected to the database */

$stmt = mysqli_prepare($link, "INSERT INTO table VALUES (?, ?, 100)"); /* Query 1 */
mysqli_stmt_bind_param($stmt, "si", $string, $integer);
mysqli_stmt_execute($stmt);
mysqli_stmt_close($stmt); // CLOSE $stmt

$stmt = mysqli_prepare($link, "INSERT INTO table VALUES ('PHP', ?, ?)"); /* Query 2 */
mysqli_stmt_bind_param($stmt, "ii", $integer, $code);
mysqli_stmt_execute($stmt);
mysqli_stmt_close($stmt); // CLOSE $stmt

/* Script A -- Continues on... */
?>

Next, we have Script B, calling mysqli_prepare again before issuing mysqli_stmt_close on the prior statement.
<?php
/* Script B -- We are already connected to the database */

$stmt = mysqli_prepare($link, "INSERT INTO table VALUES (?, ?, 100)"); /* Query 1 */
mysqli_stmt_bind_param($stmt, "si", $string, $integer);
mysqli_stmt_execute($stmt);

$stmt = mysqli_prepare($link, "INSERT INTO table VALUES ('PHP', ?, ?)"); /* Query 2 */
mysqli_stmt_bind_param($stmt, "ii", $integer, $code);
mysqli_stmt_execute($stmt);

mysqli_stmt_close($stmt); // CLOSE $stmt

/* Script B -- Continues on... */
?>

Which method is more efficient and should be used by developers?
Adam 10-Aug-2006 03:03
The purpose of prepared statements is to not include data in your SQL statements. Including them in your SQL statements is NOT safe. Always use prepared statements. They are cleaner to use (code easier to read) and not prone to SQL injections.

Escaping strings to include in SQL statements doesn't work very well in some locales hence it is not safe.
codeFiend <aeontech at gmail dot com> 05-May-2006 02:47
Note that single-quotes around the parameter markers _will_ prevent your statement from being prepared correctly.
Ex:

<?php
$stmt = $mysqli->prepare("INSERT INTO City (District) VALUES ('?')");
echo $stmt->param_count." parameters\n";
?>
will print 0 and fail with "Number of variables doesn't match number of parameters in prepared statement" warning when you try to bind the variables to it.

But

<?php
$stmt = $mysqli->prepare("INSERT INTO City (District) VALUES (?)");
echo $stmt->param_count." parameters\n";
?>
will print 1 and function correctly.

Very annoying, took me an hour to figure this out.
Ulf Wostner 23-Jan-2006 08:53
Here is an example using bind_param and bind_result, showing iteration over a list of cities.

Note that there's some bug-potential in cases where the query returns NULL for some parameter value,
but the bind_result variables still might be bound.  So, we use a conditional to spray the spot first.

$mysqli->select_db("world");

$template = "SELECT District, CountryCode FROM City WHERE Name=?";
printf("Prepare statement from template: %s\n",  $template);

$cities = array('San Francisco', 'Lisbon', 'Lisboa', 'Marrakech', 'Madrid');
printf("Cities: %s\n", join(':', $cities));

if ($stmt = $mysqli->prepare($template)) {

   foreach($cities as $city) {
     // bind the string $city to the '?'
     $stmt->bind_param("s", $city);
     $stmt->execute();
     // bind result variables
     $stmt->bind_result($d,$cc);
     // 'Lisbon' is not found in the world.City table, but 'Lisboa' is.
     // Using a conditional we avoid putting Lisbon in California.
     if($stmt->fetch()) {
       printf("%s is in  %s, %s\n", $city, $d, $cc);
     }

   }
   $stmt->close();
}

With the conditional statement we get the desired result:

Prepare statement from template: SELECT District,CountryCode FROM City WHERE Name=?
Cities: San Francisco:Lisbon:Lisboa:Marrakech:Madrid

San Francisco is in  California, USA
Lisboa is in  Lisboa, PRT
Marrakech is in  Marrakech-Tensift-Al, MAR
Madrid is in  Madrid, ESP

But, without the conditional statement we would put Lisbon in California:

San Francisco is in  California, USA
Lisbon is in  California, USA
Lisboa is in  Lisboa, PRT
Marrakech is in  Marrakech-Tensift-Al, MAR
Madrid is in  Madrid, ESP
David Kramer 20-Dec-2005 12:50
I don't think these are good examples, because the primary use of prepared queries is when you are going to call the same query in a loop, plugging in different values each time.  For instance, if you were generating a report and needed to run the same query for each line, tweaking the values in the WHERE clause, or importing data from another system.