PDOStatement::execute
Note that PDO::ATTR_STRINGIFY_FETCHES will NOT work for the MySQL driver. MySQL will always return strings because that is the behaviour of the core mysql PHP extension. See http://bugs.php.net/bug.php?id=44341
PDOStatement::fetch
(PHP 5 >= 5.1.0, PECL pdo >= 0.1.0)
PDOStatement::fetch — Obtiene la siguiente fila de un conjunto de resultados
Descripción
mixed PDOStatement::fetch
([ int
$fetch_style
[, int $cursor_orientation = PDO::FETCH_ORI_NEXT
[, int $cursor_offset = 0
]]] )
Obtiene una fila de un conjunto de resultados asociado al objeto PDOStatement. El
parámetro fetch_style determina cómo PDO devuelve
la fila.
Parámetros
-
fetch_style -
Controla cómo se devolverá la siguiente fila al llamador. Este valor debe ser una de las constantes PDO::FETCH_*, estando predeterminado PDO::ATTR_DEFAULT_FETCH_MODE (el cual por defecto es PDO::FETCH_BOTH).
PDO::FETCH_ASSOC: devuelve un array indexado por los nombres de las columnas del conjunto de resultados.
PDO::FETCH_BOTH (predeterminado): devuelve un array indexado tanto por nombre de columna, como numéricamente con índice de base 0 tal como fue devuelto en el conjunto de resultados.
PDO::FETCH_BOUND: devuelve
TRUEy asigna los valores de las columnas del conjunto de resultados a las variables de PHP a las que fueron vinculadas con el método PDOStatement::bindColumn().PDO::FETCH_CLASS: devuelve una nueva instancia de la clase solicitada, haciendo corresponder las columnas del conjunto de resultados con los nombres de las propiedades de la clase. Si
fetch_styleincluye PDO::FETCH_CLASSTYPE (por ejemplo, PDO::FETCH_CLASS | PDO::FETCH_CLASSTYPE), entonces el nombre de la clase se determina a partir del valor de la primera columna.PDO::FETCH_INTO: actualiza una instancia existente de la clase solicitada, haciendo coincidir el nombre de las columnas con los nombres de las propiedades de la clase.
PDO::FETCH_LAZY: combina PDO::FETCH_BOTH y PDO::FETCH_OBJ, creando los nombres de la variables del objeto tal como se accedieron.
PDO::FETCH_NUM: devuelve un array indexado por el número de columna tal como fue devuelto en el conjunto de resultados, comenzando por la columna 0.
PDO::FETCH_OBJ: devuelve un objeto anónimo con nombres de propiedades que se corresponden a los nombres de las columnas devueltas en el conjunto de resultados.
-
cursor_orientation -
Para un objeto PDOStatement que represente un cursor desplazable, este valor determina qué columna será devuelta por el llamador. Este valor debe ser una de las constantes PDO::FETCH_ORI_*, siendo la predeterminada PDO::FETCH_ORI_NEXT. Para solicitar un cursor desplazable para el objeto PDOStatement, se debe establecer el atributo PDO::ATTR_CURSOR a PDO::CURSOR_SCROLL cuando se prepare la sentencia SQL con PDO::prepare().
-
offset -
Para un objeto PDOStatement que represente un cursor desplazable para el cual el parámetro cursor_orientation está establecido a PDO::FETCH_ORI_ABS, este valor especifica el número absoluto de la fila del conjunto de resultados que se desea obtener.
Para un objeto PDOStatement que represente un cursor desplazable para el cual el parámetro cursor_orientation está establecido a PDO::FETCH_ORI_REL, este valor especifica la fila a obtener relativa a la posición del cursor antes de que se llame a PDOStatement::fetch().
Valores devueltos
El valor de retorno de esta función en caso de éxito depende del tipo de obtención. En
todos los casos, se devuelve FALSE en caso de error.
Ejemplos
Ejemplo #1 Obtención de filas usando diferentes tipos de obtención
<?php
$gsent = $gbd->prepare("SELECT name, colour FROM fruit");
$gsent->execute();
/* Prueba de tipos de PDOStatement::fetch */
print("PDO::FETCH_ASSOC: ");
print("Devolver la siguiente fila como un array indexado por nombre de colunmna\n");
$result = $gsent->fetch(PDO::FETCH_ASSOC);
print_r($result);
print("\n");
print("PDO::FETCH_BOTH: ");
print("Devolver la siguiente fila como un array indexado por nombre y número de columna\n");
$result = $gsent->fetch(PDO::FETCH_BOTH);
print_r($result);
print("\n");
print("PDO::FETCH_LAZY: ");
print("Devolver la siguiente fila como un objeto anónimo con nombres de columna como propiedades\n");
$result = $gsent->fetch(PDO::FETCH_LAZY);
print_r($result);
print("\n");
print("PDO::FETCH_OBJ: ");
print("Devolver la siguiente fila como un objeto anónimo con nombres de columna como propiedades\n");
$result = $gsent->fetch(PDO::FETCH_OBJ);
print $result->NAME;
print("\n");
?>
El resultado del ejemplo sería:
PDO::FETCH_ASSOC: Devolver la siguiente fila como un array indexado por nombre de colunmna
Array
(
[NAME] => apple
[COLOUR] => red
)
PDO::FETCH_BOTH: Devolver la siguiente fila como un array indexado por nombre y número de columna
Array
(
[NAME] => banana
[0] => banana
[COLOUR] => yellow
[1] => yellow
)
PDO::FETCH_LAZY: Devolver la siguiente fila como un objeto anónimo con nombres de columna como propiedades
PDORow Object
(
[NAME] => orange
[COLOUR] => orange
)
PDO::FETCH_OBJ: Devolver la siguiente fila como un objeto anónimo con nombres de columna como propiedades
kiwi
Ejemplo #2 Obtener filas con un cursor desplazable
<?php
function leerDatosHaciaAdelante($gbd) {
$sql = 'SELECT hand, won, bet FROM mynumbers ORDER BY BET';
try {
$sentencia = $gbd->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL));
$sentencia->execute();
while ($fila = $sentencia->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_NEXT)) {
$datos = $fila[0] . "\t" . $fila[1] . "\t" . $fila[2] . "\n";
print $datos;
}
$sentencia = null;
}
catch (PDOException $e) {
print $e->getMessage();
}
}
function leerDatosHaciaAtrás($gbd) {
$sql = 'SELECT hand, won, bet FROM mynumbers ORDER BY bet';
try {
$sentencia = $gbd->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL));
$sentencia->execute();
$fila = $sentencia->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_LAST);
do {
$datos = $fila[0] . "\t" . $fila[1] . "\t" . $fila[2] . "\n";
print $datos;
} while ($fila = $sentencia->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_PRIOR));
$sentencia = null;
}
catch (PDOException $e) {
print $e->getMessage();
}
}
print "Leyendo hacia adelante:\n";
leerDatosHaciaAdelante($conexión);
print "Leyendo hacia atrás:\n";
leerDatosHaciaAtrás($conexión);
?>
El resultado del ejemplo sería:
Reading forwards: 21 10 5 16 0 5 19 20 10 Reading backwards: 19 20 10 16 0 5 21 10 5
Ver también
- PDO::prepare() - Prepara una sentencia para su ejecución y devuelve un objeto sentencia
- PDOStatement::execute() - Ejecuta una sentencia preparada
- PDOStatement::fetchAll() - Devuelve un array que contiene todas las filas del conjunto de resultados
- PDOStatement::fetchColumn() - Devuelve una única columna de la siguiente fila de un conjunto de resultados
- PDOStatement::fetchObject() - Obtiene la siguiente fila y la devuelve como un objeto
- PDOStatement::setFetchMode() - Establece el modo de obtención para esta sentencia
add a note
User Contributed Notes
PDOStatement::fetch - [22 notes]
josh ¶
5 years ago
gergo at gergoerdosi dot com ¶
3 months ago
When using PDO::FETCH_COLUMN in a while loop, it's not enough to just use the value in the while statement as many examples show:
<?php
while ($row = $stmt->fetch(PDO::FETCH_COLUMN)) {
print $row;
}
?>
If there are 5 rows with values 1 2 0 4 5, then the while loop above will stop at the third row printing only 1 2. The solution is to either explicitly test for false:
<?php
while (($row = $stmt->fetch(PDO::FETCH_COLUMN)) !== false) {
print $row;
}
?>
Or use foreach with fetchAll():
<?php
foreach ($stmt->fetchAll(PDO::FETCH_COLUMN) as $row) {
print $row;
}
?>
Both will correctly print 1 2 0 4 5.
henry at henrysmith dot org ¶
1 year ago
Someone's already pointed out that PDO::CURSOR_SCROLL isn't supported by the SQLite driver. It's also worth noting that it's not supported by the MySQL driver either.
In fact, if you try to use scrollable cursors with a MySQL statement, the PDO::FETCH_ORI_ABS parameter and the offset given to fetch() will be silently ignored. fetch() will behave as normal, returning rows in the order in which they came out of the database.
It's actually pretty confusing behaviour at first. Definitely worth documenting even if only as a user-added note on this page.
lod ¶
4 years ago
A quick one liner to get the first entry returned. This is nice for very basic queries.
<?php
$count = current($db->query("select count(*) from table")->fetch());
?>php
Ome Ko ¶
1 year ago
Don't do
if($objStatement->fetch()) return $objStatement->fetch();
You want
if($blah=$objStatement->fetch()) return $blah;
Trust me on this one.
public at grik dot net ¶
2 years ago
When fetching an object, the constructor of the class is called after the fields are populated by default.
PDO::FETCH_PROPS_LATE is used to change the behaviour and make it work as expected - constructor be called _before_ the object fields will be populated with the data.
sample:
<?php
$a = $PDO->query('select id from table');
$a->setFetchMode(PDO::FETCH_CLASS|PDO::FETCH_PROPS_LATE, 'ClassName');
$obj = $a->fetch();
?>
http://bugs.php.net/bug.php?id=53394
Alex ¶
1 year ago
It seems that if you do a $statement->query() with an INSERT statement and after that a $statement->fetch() you will get an exception saying: SQLSTATE[HY000]: General error.
sumariva at gmail dot com ¶
10 months ago
I could use PDO::FETCH_COLUMN to retrieve the first column from result.
$ps->fetch( PDO::FETCH_COLUMN );
Worked on Postgresql with PHP 5.3.10.
Typer85 at gmail dot com ¶
3 years ago
Here is quick note for developers that use the PDO SQLite Driver:
The PDO SQLite driver does not support cursors, so using the PDO::CURSOR_SCROLL Attribute, will not work when using the PDO SQLite driver. For example:
<?php
// Assuming $Handle Is a PDO Handle.
$Statement = $Handle->query( $sqlStatement , array( PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL ) );
?>
What is even worse is that PDO::prepare will NOT throw an Exception when it fails to prepare the query, even when the error mode is set to throw Exceptions, and will instead return a Boolean False!
Not only do I consider this a poor design choice, but also its a real shame that this is not documented anywhere in the manual -- in fact the manual is not clear on what Attributes are supported by which drivers and which are not so developers are left to play a classic game of guess.
I hope this saves some developers some headaches.
Good Luck,
lozitskiys at gmail dot com ¶
4 years ago
I spent some hours trying to find out how to manipulate with BLOB fields using PDO.
Remember that you can't retreive BLOB data using something like this :
<?php
$sql = 'SELECT * FROM sometable LIMIT 1';
$stmt = $dbh->prepare($sql);
$stmt->execute();
$stmt->setAttribute(PDO::FETCH_ASSOC);
$row = $stmt->fetch();
$myFile = $row['file'];
?>
Instead of this you should try following approach:
<?php
$sql = "SELECT mime, file FROM sometable LIMIT 1";
$stmt = $dbh->prepare($sql);
$stmt->execute();
$stmt->bindColumn(1, $mime,);
$stmt->bindColumn(2, $file, PDO::PARAM_LOB);
$stmt->fetch();
header('Content-type: '.$mime);
print $file;
?>
Gerard van Beek ¶
5 years ago
If you to use a new instance of a class for a record you can use:
<?php
include_once("user.class");
$sth = $db->prepare("SELECT * FROM user WHERE id = 1");
/* create instance automatically */
$sth->setFetchMode( PDO::FETCH_CLASS, 'user');
$sth->execute();
$user = $sth->fetch( PDO::FETCH_CLASS );
$sth->closeCursor();
print ($user->id);
/* or create an instance yourself and use it */
$user= new user();
$sth->setFetchMode( PDO::FETCH_INTO, $user);
$sth->execute();
$user= $sth->fetch( PDO::FETCH_INTO );
$sth->closeCursor();
print ($user->id);
?>
BaBna ¶
5 years ago
When you do a SELECT query for one row, and want to check if it's there, you don't need to count the fetchAll() result, you can just check if $result->fetch() is true:
<?php
$bbnq = sprintf("SELECT login
FROM users
WHERE id = %u",27);
try
{ $req = $db_bbn->query($bbnq); }
catch (Exception $e)
{ bbnf_pdo_error($e,__FILE__,__LINE__); }
if ( $r = $req->fetch() )
{ echo "This query has a row result"; }
else
{ echo "This query has an empty result"; }
?>
marcini ¶
6 years ago
Be careful with fetch() when you use prepared statements and MySQL (I don`t know how it is with other databases). Fetch won`t close cursor and won`t let you send any other query, even if your result set has only one row, .
If you use $statement->fetch(), you will also have to use $statement->closeCursor() afterwards, to be albe to execute another query.
Alternatively you can use $statement->fetchAll() without $statement->closeCursor().
terry at bitsoup dot com ¶
7 years ago
WARNING:
fetch() does NOT adhere to SQL-92 SQLSTATE standard when dealing with empty datasets.
Instead of setting the errorcode class to 20 to indicate "no data found", it returns a class of 00 indicating success, and returns NULL to the caller.
This also prevents the exception mechainsm from firing.
Programmers will need to explicitly code tests for empty resultsets after any fetch*() instead of relying on the default behavior of the RDBMS.
I tried logging this as a bug, but it was dismissed as "working as intended". Just a head's up.
avinoamr at gmail dot com ¶
7 years ago
Note that using the FETCH_CLASS mechanism does NOT trigger the class's constructor! You must explicity instantiate the class to use it's constructor behavior.
fh at ez dot no ¶
7 years ago
I can also add that the constructor is run _after_ the data is set on the object if yo use PDO::FETCH_CLASS.
fh at ez dot no ¶
7 years ago
If you want to use PDO::FETCH_CLASS you need to set it up with setFetchMode first like so:
$stmt->setFetchMode( PDO::FETCH_CLASS, 'classType', array( 'parameters to constructor' );
$object = $stmt->fetch( PDO::FETCH_CLASS );
If you ommit this PHP will segfault.
aledmb at gmail dot com ¶
7 years ago
note that fetch constants are not included in the PDO class for PHP versions prior to 5.1
Negative Black ¶
2 years ago
When fetching multiple rows into an object. It is necessary to clone the objects returned by the PDOStatement::fetch() operation. Otherwise you will just get a list of pointers to the object located inside the statement, containing the information of the last row.
Example:
<?php
$stmt = $pdoLink->prepare("SELECT * FROM `table`;");
$stmt->setFetchMode(PDO::FETCH_INTO, new myClass());
$stmt->execute();
// Assuming there are multiple rows in the table.
while ($object = $stmt->fetch()) {
$result[] = clone $object;
}
var_dump($result);
?>
Typer85 at gmail dot com ¶
3 years ago
Just thought I would point out something interesting that caught my eye.
Once you retrieve a PDOStatement, whether for a prepared statement or a normal result set, the connection status of your PDO handle is no longer taken into consideration!
The PHP Manual clearly states that to open a PDO connection, create a new Instance of the PDO Class. To close a PDO connection, destroy the Instance, possibly by setting it to a Null Reference. The PDO Instance in this case is your handle.
Here is the interesting part. If you close the PDO connection, as described above, you can still continue to either execute a prepared statement or iterate through a result set!
For example, the following code will work perfectly fine:
<?php
// Open Handle.
$Handle = new PDO( 'mysql:host=localhost; dbname=LOG' , 'root' );
$Handle->setAttribute( PDO::ATTR_ERRMODE , PDO::ERRMODE_EXCEPTION );
// Prepare Statement.
$Statement = $Handle->prepare( "SELECT * FROM ERROR" );
// Close Handle.
$Handle = null;
// Execute Statement. Amazing How There Is No Problem Even Though The Connection Is Closed!
$Statement->execute();
// Iterate Result. Again, Amazing How There Is No Problem!
while( $row = $Statement->fetch( PDO::FETCH_BOTH , PDO::FETCH_ORI_NEXT ) ) {
}
?>
You do not even need to prepare a statement. A native query also has no problems, like the following code:
<?php
// Open Handle.
$Handle = new PDO( 'mysql:host=localhost; dbname=LOG' , 'root' );
$Handle->setAttribute( PDO::ATTR_ERRMODE , PDO::ERRMODE_EXCEPTION );
// Query Statement.
$Statement = $Handle->query( "SELECT * FROM ERROR" );
// Close Handle.
$Handle = null;
// Iterate Result.
$Statement->fetchAll( );
?>
I am not sure if this is a bug or not but its a big gottcha for developers coming from other envrionments, such as .NET or even those PHP developers used to using the native database functions before PDO came around.
For example, using the native mysql_* Functions, the following will not work:
<?php
mysql_connect( "localhost" , "root");
mysql_select_db( "LOG" );
mysql_close( );
mysql_query( "SELECT * FROM ERROR" );
?>
Good Luck,
dj UNDERSCORE robe AT hotmail DOT com ¶
3 years ago
A word of caution regarding fh at ez dot no's note: as of PHP 5.2.12 the constructor is called *before* the data is set in FETCH_CLASS mode. The previous behaviour seems to be considered a bug (http://bugs.php.net/bug.php?id=49521), so don't rely on it.
daltenho at yahoo dot com ¶
5 years ago
As an alternative to marcini's suggestion:
You can use:
$dbh->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, true);
...on your PDO connection object to allow query buffering in MySQL. This will eliminate the problem of re-preparing an unclosed statement object.