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.

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 =)

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.

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.

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.

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
*/
?>

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();
?>

Unfortunately, the use "/* bind result variables */ $stmt->bind_result($district);" is obsolete and condemned.

<?php
$mysqli = new mysqli("localhost", "test", "test", "test");
if ($mysqli->character_set_name()!="utf8mb4") { $mysqli->set_charset("utf8mb4"); }
$secondname = "Ma%";
$types = "s";
$parameters = array($secondname);
$myquery = "select * from users where secondname like ?";
if ($stmt = $mysqli->prepare($myquery)) { 
  $stmt->bind_param($types, ...$parameters);
  $stmt->execute();
  $result = $stmt->get_result();
  $stmt->close();
  $numrows = $result->num_rows;
  while($row = $result->fetch_assoc()) {
    echo $row['firstname']." ".$row['secondname']."<br />";
  }
}
$mysqli->close();
?>

Also, instead of '$stmt->bind_param("s", $city);', use "$stmt->bind_param($types, ...$parameters);" with array. Here the advantage of using an array ($parameters) is already obvious, instead of 5 variables, one array of 5 elements is used.

<?php
$mysqli = new mysqli("localhost", "test", "test", "test");
if ($mysqli->character_set_name()!="utf8mb4") { $mysqli->set_charset("utf8mb4"); }
$uid = intval($_POST['uid']);
$length=15; $account = mb_substr(trim($_POST['account']),0,$length,"utf-8"); $account=strip_tags($account);
$length=50; $password = mb_substr(trim($_POST['password']),0,$length,"utf-8"); $password = password_hash($password, PASSWORD_DEFAULT);
$length=25; $prijmeni = mb_substr(trim($_POST['prijmeni']),0,$length,"utf-8"); $prijmeni=strip_tags($prijmeni);
$length=25; $firstname = mb_substr(trim($_POST['firstname']),0,$length,"utf-8"); $firstname=strip_tags($firstname); $firstname = str_replace(array(">","<",'"'), array("","",""), $firstname); 
$dotaz = "UPDATE users SET account = ?, password = ?, secname = ?, firstname = ? WHERE uid = ?";
$types = "ssssi";
$parameters = array($account,$password,$prijmeni,$firstname,$uid);
if ($stmt = $mysqli->prepare($dotaz)) {
  $stmt->bind_param($types, ...$parameters);
  $stmt->execute();
  echo $stmt->affected_rows;
  $stmt->close();
}
$mysqli->close();
?>

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.

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

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.

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
?>

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.

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.

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;
    }
}
?>

All data must be fetched before a new statement prepare

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.

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.

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.

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);