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The MySQLi class

<<mysqli::poll -- mysqli_poll

mysqli::query -- mysqli_query>>

mysqli::prepare

mysqli_prepare

(PHP 5)

mysqli::prepare -- mysqli_preparePrepare an SQL statement for execution

Beschreibung

Objektorientierter Stil

mysqli_stmt mysqli::prepare ( string $query )

Prozeduraler Stil

mysqli_stmt mysqli_prepare ( mysqli $link , string $query )

Prepares the SQL query, and returns a statement handle to be used for further operations on the statement. The query must consist of a single SQL statement.

The parameter markers must be bound to application variables using mysqli_stmt_bind_param() and/or mysqli_stmt_bind_result() before executing the statement or fetching rows.

Parameter-Liste

link

Nur bei prozeduralem Aufruf: Ein von mysqli_connect() oder mysqli_init() zurückgegebenes Verbindungsobjekt.

query

The query, as a string.

Hinweis:

You should not add a terminating semicolon or \g to the statement.

This parameter can include one or more parameter markers in the SQL statement by embedding question mark (?) characters at the appropriate positions.

Hinweis:

The markers are legal only in certain places in SQL statements. For example, they are allowed 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 allowed for identifiers (such as table or column names), in the select list that names the columns to be returned by a SELECT statement, or to specify both operands of a binary operator such as the = equal sign. The latter restriction is necessary because it would be impossible to determine the parameter type. It's not allowed to compare marker with NULL by ? IS NULL too. In general, parameters are legal only in Data Manipulation Language (DML) statements, and not in Data Definition Language (DDL) statements.

Rückgabewerte

mysqli_prepare() returns a statement object or FALSE if an error occurred.

Beispiele

Beispiel #1 mysqli::prepare() example

Objektorientierter Stil

<?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 */
if ($stmt $mysqli->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);

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

/* close connection */
$mysqli->close();
?>

Prozeduraler Stil

<?php
$link 
mysqli_connect("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 */
if ($stmt mysqli_prepare($link"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);

    
/* close statement */
    
mysqli_stmt_close($stmt);
}

/* close connection */
mysqli_close($link);
?>

The above examples will output:

Amersfoort is in district Utrecht

Siehe auch


9 BenutzerBeiträge:
- Beiträge aktualisieren...
Domenic Denicola
10.01.2010 16:18
It's worth noting that this function will error out with "Number of variables doesn't match number of parameters in prepared statement" for reasons that have nothing to do with the number of variables and parameters.

For example, I made the newbie mistake of saying "SELECT (username, password) FROM mytable WHERE something = ?" instead of "SELECT username, password FROM mytable WHERE something = ?" and got that error.

So basically, if you get that error, check your query syntax very carefully before poking around for the various problems that could occur with binding, pass-by-reference, etc.
sdepouw at NOSPAM dot com
30.07.2009 3:03
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
30.09.2008 1:44
All data must be fetched before a new statement prepare
admin at xorath dot com
15.08.2007 19:39
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
25.05.2007 21:30
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
11.08.2006 0:03
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
5.05.2006 23:47
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
23.01.2006 17:53
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
20.12.2005 21:50
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.



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