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mysqli_stmt::prepare

mysqli_stmt_prepare

(PHP 5, PHP 7, PHP 8)

mysqli_stmt::prepare -- mysqli_stmt_prepare — Prepares an SQL statement for execution

Descrizione

Stile orientato agli oggetti

public mysqli_stmt::prepare(string $query): bool

Stile procedurale

mysqli_stmt_prepare(mysqli_stmt $statement, string $query): bool

Prepares a statement for execution. The query must consist of a single SQL statement.

The statement template can contain zero or more question mark (?) parameter markers⁠—also called placeholders. The parameter markers must be bound to application variables using mysqli_stmt_bind_param() before executing the statement.

Nota:
In the case where a statement is passed to mysqli_stmt_prepare() that is longer than max_allowed_packet of the server, the returned error codes are different depending on whether you are using MySQL Native Driver (mysqlnd) or MySQL Client Library (libmysqlclient). The behavior is as follows:

mysqlnd on Linux returns an error code of 1153. The error message means got a packet bigger than max_allowed_packet bytes.

mysqlnd on Windows returns an error code 2006. This error message means server has gone away.

libmysqlclient on all platforms returns an error code 2006. This error message means server has gone away.

Elenco dei parametri

stmt

Solo nello stile procedurale: un identificatore di statement restituito da mysqli_stmt_init().

query

The query, as a string. It must consist of a single SQL statement.

The SQL statement may contain zero or more parameter markers represented by question mark (?) characters at the appropriate positions.

Nota:
The markers are legal only in certain places in SQL statements. For example, they are permitted in the VALUES() list of an INSERT statement (to specify column values for a row), or in a comparison with a column in a WHERE clause to specify a comparison value. However, they are not permitted for identifiers (such as table or column names).

Valori restituiti

Restituisce true in caso di successo, false in caso di fallimento.

Errori/Eccezioni

If mysqli error reporting is enabled (MYSQLI_REPORT_ERROR) and the requested operation fails, a warning is generated. If, in addition, the mode is set to MYSQLI_REPORT_STRICT, a mysqli_sql_exception is thrown instead.

Esempi

Example #1 mysqli_stmt::prepare() example

Stile orientato agli oggetti

<?php

mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");

$city = "Amersfoort";

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

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

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

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

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

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

Stile procedurale

<?php

mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$link = mysqli_connect("localhost", "my_user", "my_password", "world");

$city = "Amersfoort";

/* create a prepared statement */
$stmt = mysqli_stmt_init($link);
mysqli_stmt_prepare($stmt, "SELECT District FROM City WHERE Name=?");

/* bind parameters for markers */
mysqli_stmt_bind_param($stmt, "s", $city);

/* execute query */
mysqli_stmt_execute($stmt);

/* bind result variables */
mysqli_stmt_bind_result($stmt, $district);

/* fetch value */
mysqli_stmt_fetch($stmt);

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

I precedenti esempi visualizzeranno:

Amersfoort is in district Utrecht

Vedere anche:

mysqli_stmt_init() - Initializes a statement and returns an object for use with mysqli_stmt_prepare
mysqli_stmt_execute() - Executes a prepared statement
mysqli_stmt_fetch() - Fetch results from a prepared statement into the bound variables
mysqli_stmt_bind_param() - Binds variables to a prepared statement as parameters
mysqli_stmt_bind_result() - Binds variables to a prepared statement for result storage
mysqli_stmt_get_result() - Gets a result set from a prepared statement as a mysqli_result object
mysqli_stmt_close() - Closes a prepared statement

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User Contributed Notes 9 notes

down

logos-php at kith dot org ¶

12 years ago


Note that if you're using a question mark as a placeholder for a string value, you don't surround it with quotation marks in the MySQL query.

For example, do this:

mysqli_stmt_prepare($stmt, "SELECT * FROM foo WHERE foo.Date > ?");

Do not do this:

mysqli_stmt_prepare($stmt, "SELECT * FROM foo WHERE foo.Date > '?'");

If you put quotation marks around a question mark in the query, then PHP doesn't recognize the question mark as a placeholder, and then when you try to use mysqli_stmt_bind_param(), it gives an error to the effect that you have the wrong number of parameters.

The lack of quotation marks around a string placeholder is implicit in the official example on this page, but it's not explicitly stated in the docs, and I had trouble figuring it out, so figured it was worth posting.

down

logos-php at kith dot orgpp ¶

12 years ago


Turns out you can't directly use a prepared statement for a query that has a placeholder in an IN() clause.

There are ways around that (such as constructing a string that consists of n question marks separated by commas, then using that set of placeholders in the IN() clause), but you can't just say IN (?).

This is a MySQL restriction rather than a PHP restriction, but it's not really documented in the MySQL docs either, so I figured it was worth mentioning here.

(Btw, turns out someone else had previously posted the info that I put in my previous comment, about not using quotation marks. Sorry for the repeat; not sure how I missed the earlier comment.)

down

ndungi at gmail dot com ¶

15 years ago


The `prepare` , `bind_param`, `bind_result`, `fetch` result, `close` stmt cycle can be tedious at times. Here is an object that does all the mysqli mumbo jumbo for you when all you want is a select leaving you to the bare essential `preparedSelect` on a prepared stmt. The method returns the result set as a 2D associative array with the `select`ed columns as keys. I havent done sufficient error-checking and it also may have some bugs. Help debug and improve on it. 

I used the bible.sql db from http://www.biblesql.net/sites/biblesql.net/files/bible.mysql.gz.

Baraka tele!

============================

<?php

class DB
{
    public $connection;
    
    #establish db connection
    public function __construct($host="localhost", $user="user", $pass="", $db="bible")
    {
        $this->connection = new mysqli($host, $user, $pass, $db);
                  
        if(mysqli_connect_errno())
        {
            echo("Database connect Error : " 
            . mysqli_connect_error($mysqli));
        }    
    }
    
    #store mysqli object
    public function connect()
    {
        return $this->connection;
    }

    #run a prepared query
    public function runPreparedQuery($query, $params_r)
    {
        $stmt = $this->connection->prepare($query);
        $this->bindParameters($stmt, $params_r);

        if ($stmt->execute()) {
            return $stmt;
        } else {
            echo("Error in $statement: " 
                      . mysqli_error($this->connection));
            return 0;
        }
        
    }

 # To run a select statement with bound parameters and bound results. 
 # Returns an associative array two dimensional array which u can easily  
 # manipulate with array functions.
 
    public function preparedSelect($query, $bind_params_r)
    {
        $select = $this->runPreparedQuery($query, $bind_params_r);
        $fields_r = $this->fetchFields($select);
        
        foreach ($fields_r as $field) {
            $bind_result_r[] = &${$field};
        } 
        
        $this->bindResult($select, $bind_result_r);
        
        $result_r = array();
        $i = 0;
        while ($select->fetch()) {
            foreach ($fields_r as $field) {
                $result_r[$i][$field] = $$field;
            }
            $i++;
        }
        $select->close();
        return $result_r;    
    }
    
    
    #takes in array of bind parameters and binds them to result of 
    #executed prepared stmt
    
    private function bindParameters(&$obj, &$bind_params_r)
    {
        call_user_func_array(array($obj, "bind_param"), $bind_params_r);
    }
    
    private function bindResult(&$obj, &$bind_result_r)
    {
        call_user_func_array(array($obj, "bind_result"), $bind_result_r);
    }
    
    #returns a list of the selected field names
    
    private function fetchFields($selectStmt)
    {
        $metadata = $selectStmt->result_metadata();
        $fields_r = array();
        while ($field = $metadata->fetch_field()) {
            $fields_r[] = $field->name;
        }

        return $fields_r;
    }
}
#end of class
 
#An example of the DB class in use

$DB = new DB("localhost", "root", "", "bible");
$var = 5; 
$query = "SELECT abbr, name from books where id > ?" ;
$bound_params_r = array("i", $var);

$result_r = $DB->preparedSelect($query, $bound_params_r);

#loop thru result array and display result

foreach ($result_r as $result) {
    echo $result['abbr'] . " : " . $result['name'] . "<br/>" ;
}

?>

down

andrey at php dot net ¶

19 years ago


If you select LOBs use the following order of execution or you risk mysqli allocating more memory that actually used



1)prepare()

2)execute()

3)store_result()

4)bind_result()



If you skip 3) or exchange 3) and 4) then mysqli will allocate memory for the maximal length of the column which is 255 for tinyblob, 64k for blob(still ok), 16MByte for MEDIUMBLOB - quite a lot and 4G for LONGBLOB (good if you have so much memory). Queries which use this order a bit slower when there is a LOB but this is the price of not having memory exhaustion in seconds.

down

kontakt at arthur minus schiwon dot de ¶

16 years ago


If you wrap the placeholders with quotation marks you will experience warnings like "Number of variables doesn't match number of parameters in prepared statement" (at least with INSERT Statements).

down

mhradek AT gmail.com ¶

16 years ago


A particularly helpful adaptation of this function and the call_user_func_array function:

// $params is sent as array($val=>'i', $val=>'d', etc...)

function db_stmt_bind_params($stmt, $params)
{ 
    $funcArg[] = $stmt; 
    foreach($params as $val=>$type)
    { 
        $funcArg['type'] .= $type; 
        $funcArg[] = $val; 
    } 
    return call_user_func_array('mysqli_stmt_bind_param', $funcArgs); 
} 

Thanks to 'sned' for the code.

down

st dot john dot johnson at gmail dot com ¶

17 years ago


In reference to what lachlan76 said before, stored procedures CAN be executed through prepared statements as long as you tell the DB to move to the next result before executing again.



Example (Five calls to a stored procedure):



<?php

for ($i=0;$i<5;$i++) {

  $statement = $mysqli->stmt_init();

  $statement->prepare("CALL some_procedure( ? )");



  // Bind, execute, and bind.

  $statement->bind_param("i", 1);

  $statement->execute();

  $statement->bind_result($results);



  while($statement->fetch()) {

    // Do what you want with your results.

  }



  $statement->close();



  // Now move the mysqli connection to a new result.

  while($mysqli->next_result()) { }

}

?>



If you include the last statement, this code should execute without the nasty "Commands out of sync" error.

down

-1

lukaszNOSPAMPLEASE at epas dot pl ¶

16 years ago


i've got some bad news for you guys if you haven't found out already.

the trick with mysqli_next_result() only prevents having the connection dropped after a stored procedure call.

apparently you can bind parameters for a prepared stored procedure call, but you'll get messed up records from mysqli_stmt_fetch() after mysqli_stmt_bind_result(), at least when the stored procedure itself contains a prepared statement.

a way to avoid data corruption could be specifying the CLIENT_MULTI_STATEMENTS flag in mysqli_real_connect(), if it wasn't disabled entirely (for security reasons, as they say). another option is to use mysqli_multi_query(), but then you can't bind at all.

down

-1

lachlan76 at gmail dot com ¶

17 years ago


Do not try to use a stored procedure through a prepared statement.



Example:



<?php

$statement = $mysqli->stmt_init();

$statement->prepare("CALL some_procedure()");

?>



If you attempt to do this, it will fail by dropping the connection during the next query.  Use mysqli_multi_query instead.



Example:



<?php

$mysqli->multi_query("CALL some_procedure()");

do

{

  $result = $mysqli->store_result();



   // Do your processing work here  

  

  $result->free();

} while($mysqli->next_result());

?>



This means that you cannot bind parameters or results, however.

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