PDO::prepare

(PHP 5 >= 5.1.0, PHP 7, PHP 8, PHP 8,PECL pdo >= 0.1.0)

PDO::prepare — Prépare une requête à l'exécution et retourne un objet

Description

public PDO::prepare(string $query, array $options = []): PDOStatement|false

Prépare une requête SQL à être exécutée par la méthode PDOStatement::execute(). Le modèle de déclaration peut contenir zéro ou plusieurs paramètres nommés (:nom) ou marqueurs (?) pour lesquels les valeurs réelles seront substituées lorsque la requête sera exécutée. L'utilisation à la fois des paramètres nommés ainsi que les marqueurs est impossible dans un modèle de déclaration ; seul l'un ou l'autre style de paramètre. Utilisez ces paramètres pour lier les entrées utilisateurs, ne les incluez pas directement dans la requête.

Vous devez inclure un marqueur avec un nom unique pour chaque valeur que vous souhaitez passer dans la requête lorsque vous appelez PDOStatement::execute(). Vous ne pouvez pas utiliser un marqueur avec deux noms identiques dans une requête préparée, à moins que le mode émulation ne soit actif.

Note:
Les marqueurs de paramètres peuvent représenter uniquement un littéral de données complet. Ni une partie de littéral, ni un mot clé, ni un identifiant, ni toute autre requête arbitraire ne peuvent être liés en utilisant les paramètres. Par exemple, vous ne pouvez associer plusieurs valeurs à un seul marqueur de nom entrant, dans la clause IN() d'une requête SQL.

Appeler PDO::prepare() et PDOStatement::execute() pour les requêtes qui doivent être exécutées plusieurs fois avec différentes valeurs de paramètres optimisent les performances de votre application en autorisant le pilote à négocier coté client et/ou serveur avec le cache des requêtes et les meta-informations. De plus appeler PDO::prepare() et PDOStatement::execute() aident à prévenir les attaques par injection SQL en éliminant le besoin de protéger les paramètres manuellement.

PDO émule les requêtes préparées / les paramètres liés pour les pilotes qui ne le supportent pas nativement, et peut également réécrire les paramètres nommés ou les marqueurs en quelques choses de plus approprié, si le pilote supporte un style et pas l'autre.

Note: L'analyseur utilisé pour les déclarations préparés émulées et pour réécrire les paramètres nommés ou du style point d'intérogation supporte l'échappement antislash non standard pour les guillemets simple et double. Ceci signifie que des guillemets terminant qui sont précédés par un antislash ne seront pas reconnue comme tel, ce qui peut résulter dans une mauvaise détection des paramètres causant la déclaration préparer d'échouer lorsqu'elle est exécuté. Un contournement est de ne pas utiliser les requêtes émulées pour de telles requêtes SQL, et d'éviter de réécrite les paramètres en utilisant un style de paramètre qui est supporté nativement par le pilote.

À partir de PHP 7.4.0, les points d'interrogation peuvent être échappés en les dédoublant. Cela signifie que la chaîne ?? sera traduite en ? lors de l'envoi de la requête à la base de données.

Liste de paramètres

query: Doit être un modèle de requête SQL valide pour le serveur de base de données ciblée.
options: Ce tableau contient une ou plusieurs paires clé=>valeur pour définir les valeurs des attributs pour l'objet PDOStatement que cette méthode retourne. Vous pouvez utiliser ceci pour définir la valeur PDO::ATTR_CURSOR à PDO::CURSOR_SCROLL pour demander un curseur scrollable. Quelques pilotes ont des options spécifiques qui peuvent être définies au moment de la préparation.

Valeurs de retour

Si le serveur de base de données prépare avec succès cette requête, PDO::prepare() retourne un objet PDOStatement. Si le serveur de base de données ne réussit pas à préparer la requête, PDO::prepare() retourne false ou émet une exception PDOException (suivant le gestionnaire des erreurs).

Note:
L'émulation de requêtes préparées ne communique pas avec le serveur de base de données. Aussi, la fonction PDO::prepare() ne vérifie pas la requête.

Erreurs / Exceptions

Émet une erreur de niveau E_WARNING si l'attribut PDO::ATTR_ERRMODE est défini à PDO::ERRMODE_WARNING.

Lève une exception PDOException si l'attribut PDO::ATTR_ERRMODE est défini à PDO::ERRMODE_EXCEPTION.

Exemples

Exemple #1 Modèle de déclaration SQL avec des paramètres nommés

<?php
/* Exécute une requête préparée en passant un tableau de valeurs */
$sql = 'SELECT nom, couleur, calories
    FROM fruit
WHERE calories < :calories AND couleur = :couleur';
$sth = $dbh->prepare($sql, [PDO::ATTR_CURSOR => PDO::CURSOR_FWDONLY]);
$sth->execute(['calories' => 150, 'couleur' => 'red']);
$red = $sth->fetchAll();
/* Les clés du tableau peuvent être préfixées par des deux-points ":" également (facultatif) */
$sth->execute([':calories' => 175, ':couleur' => 'yellow']);
$yellow = $sth->fetchAll();
?>

Exemple #2 Modèle de déclaration SQL avec des marqueurs

<?php
/* Exécute une requête préparée en passant un tableau de valeurs */
$sth = $dbh->prepare('SELECT nom, couleur, calories
    FROM fruit
    WHERE calories < ? AND couleur = ?');
$sth->execute([150, 'rouge']);
$red = $sth->fetchAll();
$sth->execute([175, 'jaune']);
$yellow = $sth->fetchAll();
?>

Exemple #3 Modèle de déclaration SQL avec un point d'interrogation échappé

<?php
/* note: ceci n'est valable que pour les bases de données PostgreSQL */
$sth = $dbh->prepare('SELECT * FROM issues WHERE tag::jsonb ?? ?');
$sth->execute(['feature']);
$featureIssues = $sth->fetchAll();
$sth->execute(['performance']);
$performanceIssues = $sth->fetchAll();
?>

Voir aussi

PDO::exec() - Exécute une requête SQL et retourne le nombre de lignes affectées
PDO::query() - Prépare et Exécute une requête SQL sans marque substitutive
PDOStatement::execute() - Exécute une requête préparée

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User Contributed Notes 17 notes

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182

Anonymous ¶

11 years ago

To those wondering why adding quotes to around a placeholder is wrong, and why you can't use placeholders for table or column names:

There is a common misconception about how the placeholders in prepared statements work: they are not simply substituted in as (escaped) strings, and the resulting SQL executed. Instead, a DBMS asked to "prepare" a statement comes up with a complete query plan for how it would execute that query, including which tables and indexes it would use, which will be the same regardless of how you fill in the placeholders.

The plan for "SELECT name FROM my_table WHERE id = :value" will be the same whatever you substitute for ":value", but the seemingly similar "SELECT name FROM :table WHERE id = :value" cannot be planned, because the DBMS has no idea what table you're actually going to select from.

Even when using "emulated prepares", PDO cannot let you use placeholders anywhere, because it would have to work out what you meant: does "Select :foo From some_table" mean ":foo" is going to be a column reference, or a literal string?

When your query is using a dynamic column reference, you should be explicitly white-listing the columns you know to exist on the table, e.g. using a switch statement with an exception thrown in the default: clause.

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Simon Le Pine ¶

11 years ago

Hi All,

First time posting to php.net, a little nervous.

After a bunch of searching I've learned 2 things about prepared statements:
1.) It fails if you enclose in a single quote (')
This fails: "SELECT * FROM users WHERE email=':email'"
This works: "SELECT * FROM users WHERE email=:email"
2.) You cannot search with a prepared statement
This fails: "SELECT * FROM users WHERE :search=:email"
This succeeds: "SELECT * FROM users WHERE $search=:email"

In my case I allow the user to enter their username or email, determine which they've entered and set $search to "username" or "email". As this value is not entered by the user there is no potential for SQL injection and thus safe to use as I have done.

Hope that saves someone else from a lot of searching.

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bg at enativ dot com ¶

10 years ago

if you run queries in a loop, don't include $pdo->prepare() inside the loop, it will save you some resources (and time).

prepare statement inside loop:
for($i=0; $i<1000; $i++) {
    $rs = $pdo->prepare("SELECT `id` FROM `admins` WHERE `groupID` = :groupID AND `id` <> :id");
    $rs->execute([':groupID' => $group, ':id' => $id]);
}

// took 0.066626071929932 microseconds

prepare statement outside loop:
$rs = $pdo->prepare("SELECT `id` FROM `admins` WHERE `groupID` = :groupID AND `id` <> :id");
for($i=0; $i<1000; $i++) {
    $rs->execute([':groupID' => $group, ':id' => $id]);
}

// took 0.064448118209839 microseconds

for 1,000 (simple) queries it took 0.002 microseconds less.
not much, but it worth mention.

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daniel dot egeberg at gmail dot com ¶

15 years ago

You can also pass an array of values to PDOStatement::execute(). This is also secured against SQL injection. You don't necessarily have to use bindParam() or bindValue().

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theking2 at king dot ma ¶

1 year ago

There are restrictions on the placeholder string. In the following code the first execute fails with a SQLSTATE[HY093]. It is not clear exactly what characters are allowed.

<?php declare(strict_types=1);

$db = new \PDO("mysql:hostname=localhost;dbname=minidwh", "minidwh", "Meisterstueck!");
$db->query("SET NAMES 'utf8mb4'");

$db->query("DROP TABLE IF EXISTS `äëïöüß`");
$db->query("CREATE TABLE `äëïöüß` ( `id` INT NOT NULL AUTO_INCREMENT, PRIMARY KEY (`id`) ) ENGINE = ARIA;");
$db->query("ALTER TABLE `äëïöüß` ADD COLUMN `äëïöüß` TEXT NULL");
try {
  $stmt = $db->prepare("INSERT INTO `äëïöüß` (`äëïöüß`) VALUES (:äëïöüß)");
  $result = $stmt->execute([':äëïöüß' => 'test1']);
} catch (\PDOException $e) {
  echo $e->getMessage() . '<BR>';
}

try {
  $stmt = $db->prepare("INSERT INTO `äëïöüß` (`äëïöüß`) VALUES (?)");
  $result = $stmt->execute(['test2']);
} catch (\PDOException $e) {
  echo $e->getMessage() . '<BR>';
}

try {
  $stmt = $db->prepare("INSERT INTO `äëïöüß` (`äëïöüß`) VALUES (:column)");
  $result = $stmt->execute([':column' => 'test3']);
} catch (\PDOException $e) {
  echo $e->getMessage() . '<BR>';
}

try {
  $stmt = $db->prepare("INSERT INTO `äëïöüß` (`äëïöüß`) VALUES (:column)");
  $stmt->bindValue(':column', 'test4');
  $result = $stmt->execute();
} catch (\PDOException $e) {
  echo $e->getMessage() . '<BR>';
}

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admin at wdfa dot co dot uk ¶

15 years ago

Note on the SQL injection properties of prepared statements.

Prepared statements only project you from SQL injection IF you use the bindParam or bindValue option.

For example if you have a table called users with two fields, username and email and someone updates their username you might run

UPDATE `users` SET `user`='$var'

where $var would be the user submitted text. 

Now if you did 
<?php
$a=new PDO("mysql:host=localhost;dbname=database;","root","");
$b=$a->prepare("UPDATE `users` SET user='$var'");
$b->execute();
?>

and the user had entered  User', email='test for a test the injection would occur and the email would be updated to test as well as the user being updated to User.

Using bindParam as follows
 <?php
$var="User', email='test";
$a=new PDO("mysql:host=localhost;dbname=database;","root","");
$b=$a->prepare("UPDATE `users` SET user=:var");
$b->bindParam(":var",$var);
$b->execute();
?>

The sql would be escaped and update the username to User', email='test'

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Mark Simon ¶

7 years ago

Many students are tempted to add single quotes around string place holders in the SQL statement, since that’s what they normally do around strings in SQL and PHP.

I have to explain:

Quotes are not part of the string — they are used to construct a string in the coding language. If you are creating a string literal in SQL or PHP, then it must indeed be quoted. If the string has already been created, and is being passed on, then additional quotes would be wrong at best, and mis-interpreted at worst.

In prepared place holders, think of place holders as variables, which, whether they are strings or other values, are always written without quotes.

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public at grik dot net ¶

12 years ago

With PDO_MYSQL you need to remember about the PDO::ATTR_EMULATE_PREPARES option.

The default value is TRUE, like
$dbh->setAttribute(PDO::ATTR_EMULATE_PREPARES,true); 

This means that no prepared statement is created with $dbh->prepare() call. With exec() call PDO replaces the placeholders with values itself and sends MySQL a generic query string.

The first consequence is that the call  $dbh->prepare('garbage');
reports no error. You will get an SQL error during the $dbh->exec() call.
The second one is the SQL injection risk in special cases, like using a placeholder for the table name.

The reason for emulation is a poor performance of MySQL with prepared statements. Emulation works significantly faster.

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Robin ¶

14 years ago

Use prepared statements to ensure integrity of binary data during storage and retrieval. Escaping/quoting by f.e. sqlite_escape_string() or PDO::quote() is NOT suited for binary data - only for strings of text.

A simple test verifies perfect storage and retrieval with prepared statements:

<?php

$num_values = 10000;

$db = new pdo( 'sqlite::memory:' );

$db->exec( 'CREATE TABLE data (binary BLOB(512));' );

// generate plenty of troublesome, binary data
for( $i = 0; $i < $num_values; $i++ )
{
    for( $val = null, $c = 0; $c < 512/16; $c++ )
        $val .= md5( mt_rand(), true );
    @$binary[] = $val;
}

// insert each value by prepared statement
for( $i = 0; $i < $num_values; $i++ )
    $db->prepare( 'INSERT INTO data VALUES (?);' )->execute( array($binary[$i]) );

// fetch the entire row
$data = $db->query( 'SELECT binary FROM data;' )->fetchAll( PDO::FETCH_COLUMN );

// compare with original array, noting any mismatch
for( $i = 0; $i < $num_values; $i++ )
    if( $data[$i] != $binary[$i] ) echo "[$i] mismatch\n";

$db = null;

?>

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php dot chaska at xoxy dot net ¶

11 years ago

Note that for Postgres, even though Postgres does support prepared statements, PHP's PDO driver NEVER sends the prepared statement to the Postgres server in advance of the call to PDO::execute().  

Therefore, PDO::prepare() will never throw an error for things like faulty SQL syntax.  

It also means the server will not parse and plan the SQL until the first time PDO::execute() is called, which may or may not adversely affect your optimization plans.

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pbakhuis ¶

10 years ago

Noteworthy in my opinion is that if you prepare a statement but do not bind a value to the markers it will insert null by default. e.g.
<?php
/** @var PDO $db */
$prep = $db->prepare('INSERT INTO item(title, link) VALUES(:title, :link)');
$prep->execute();
?>
Will attempt to insert null, null into the item table.

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machitgarha at outlook dot com ¶

7 years ago

Hello everyone.

I want to note that it doesn't matter where you are using a variable inside the query directly, that is not secure against SQL injections (unless performing a long security operation).

The following example is insecure against SQL injections:

<?php

$statement = $databaseConnection->prepare("SELECT * FROM `$_POST['table']` WHERE $_POST['search_for']=:search");
$statement->bindParam(":search", $search);
$search = 18; // For example
$statement->execute();

?>

If an attacker pass '1;-- ' as input named 'search_for', he is not a very bad attacker; because he didn't delete your data! In the above example, an attacker can do anything with connected database (unless you have restricted the connected user). Unfortunately, as Simon Le Pine mentioned, you cannot use prepared statements as other parts of a query; just can be used to search in indexes.

Hope this helps from loosing some data.
Sorry for my a bit weak English!

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roth at egotec dot com ¶

18 years ago

Attention using MySQL and prepared statements.
Using a placeholder multiple times inside a statement doesn't work. PDO just translates the first occurance und leaves the second one as is.

select id,name from demo_de where name LIKE :name OR name=:name

You have to use

select id,name from demo_de where name LIKE :name OR name=:name2

and bind name two times. I don't know if other databases (for example Oracle or MSSQL) support multiple occurances. If that's the fact, then the PDO behaviour for MySQL should be changed.

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-2

orrd101 at gmail dot com ¶

12 years ago

Don't just automatically use prepare() for all of your queries.

If you are only submitting one query, using PDO::query() with PDO::quote() is much faster (about 3x faster in my test results with MySQL).  A prepared query is only faster if you are submitting thousands of identical queries at once (with different data).

If you Google for performance comparisons you will find that this is generally consistently the case, or you can write some code and do your own comparison for your particular configuration and query scenario. But generally PDO::query() will always be faster except when submitting a large number of identical queries.  Prepared queries do have the advantage of escaping the data for you, so you have to be sure to use quote() when using query().

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-2

Hayley Watson ¶

11 years ago

It is possible to prepare in advance several statements against a single connection. As long as that connection remains open the statements can be executed and fetched from as often as you like in any order; their "prepare-execute-fetch" steps can be interleaved in whichever way is best.

So if you're likely to be using several statements often (perhaps within a loop of transactions), you may like to consider preparing all the statements you'll be using up front.

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-3

ak_9jsz ¶

16 years ago

Using cursors doesn't work with SQLite 3.5.9. I get an error message when it gets to the execute() method.

Some of you might be saying "duh!" but i was surprised to see TRIGGER support in SQLite, so i had to try. :)

I wanted to use Absolute referencing on a Scrollable cursor and i only wanted one column of data. So i used this instead of a cursor.

<?php

$dbo = new PDO('sqlite:tdb');
$sql = 'SELECT F1, F2 FROM tblA WHERE F1 <> "A";';
$res = $dbo->prepare($sql);
$res->execute();
$resColumn = $res->fetchAll(PDO::FETCH_COLUMN, 0);

for($r=0;$r<=3;$r++)
    echo 'Row '. $r . ' returned: ' . $resColumn[$r] . "\n";

$dbo = null;
$res = null;
?>

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-4

sgirard at rossprint dot com ¶

14 years ago

Maybe everyone else already knows this but...

If you have a routine that prepares/executes many insert or update statements for a sqlite db then you may want to make use of the pdo transactions. 

On some old hardware my query set went from 12 seconds to 1/3-1/2 second. 

-sean

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