PDOStatement::fetch

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

PDOStatement::fetch — Obtiene la siguiente fila de un conjunto de resultados

Descripción

public PDOStatement::fetch(int $mode = ?, int $cursorOrientation = PDO::FETCH_ORI_NEXT, int $cursorOffset = 0): mixed

Obtiene una fila de un conjunto de resultados asociado al objeto PDOStatement. El parámetro mode determina cómo PDO devuelve la fila.

Parámetros

mode

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 true y 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, y llamando al constructor después, a menos que también se proporcione PDO::FETCH_PROPS_LATE. Si mode incluye 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_NAMED: devuelve un array con la misma forma que PDO::FETCH_ASSOC, excepto que si hubiera múltiples columnas con el mismo nombre, el valor al que hace referencia dicha clave será un array con todos los valores de la fila de tuviera ese nombre de columna.
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.
PDO::FETCH_PROPS_LATE: cuando se usa con PDO::FETCH_CLASS, se llama al constructor de la clase antes de que las proiedades sean asignadas desde los valores de la columna respectiva.

cursorOrientation

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().

cursorOffset

Para un objeto PDOStatement que represente un cursor desplazable para el cual el parámetro cursorOrientation 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 cursorOrientation 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 o si no existen más filas por devolver.

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

Ejemplo #3 Orden de construcción

Cuando los objetos se obtienen mediante PDO::FETCH_CLASS, las propiedades del objeto se asignan primero, y luego se invoca al constructor de la clase. Si también se proporciona PDO::FETCH_PROPS_LATE, este orden se invierte, es decir, primero se llama al constructor y luego se asignan las propiedades.

<?php
class Persona
{
    private $name;

    public function __construct()
    {
        $this->decir();
    }

    public function decir()
    {
        if (isset($this->name)) {
            echo "Soy {$this->name}.\n";
        } else {
            echo "Aún no tengo nombre.\n";
        }
    }
}

$sth = $dbh->query("SELECT * FROM people");
$sth->setFetchMode(PDO::FETCH_CLASS, 'Persona');
$persona = $sth->fetch();
$persona->decir();
$sth->setFetchMode(PDO::FETCH_CLASS|PDO::FETCH_PROPS_LATE, 'Persona');
$persona = $sth->fetch();
$persona->decir();
?>

El resultado del ejemplo sería algo similar a:

Soy Alice.
Soy Alice.
Aún no tengo nombre.
Soy Bob.

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

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User Contributed Notes 26 notes

down

terry at bitsoup dot com ¶

18 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.

down

yarco dot wang at gmail dot com ¶

11 years ago


If no record, this function will also return false.
I think that is not very good...

down

henry at henrysmith dot org ¶

13 years 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.

down

gergo at gergoerdosi dot com ¶

11 years 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.

down

public at grik dot net ¶

14 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

down

lod ¶

16 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

down

Typer85 at gmail dot com ¶

14 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,

down

paulf at quillandmouse dot com ¶

4 years ago


A prior poster indicated that this function returns a NULL when there are no results. This is not true. This function returns an empty array. fetchAll() returns the same.

Also, the documentation specifies what happens on "failure", but doesn't indicate what constitutes a "failure". A "failure" could be where the function returns no results; that is, the query "failed". However, a "failure" is apparently a situation where the PDO error functions would reveal a "failure", as in illegal SQL syntax, or a query on a table which doesn't exist, etc. An empty result is not a "failure". Maybe that's obvious to everyone else, but it wasn't to me.

down

Gerard van Beek ¶

17 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);
?>

down

lenz_kappov at yahoo dot co dot uk ¶

10 years ago


Because MySQL does not currently support the use of cursors, the $cursor_offset feature cannot work when using PDO to access a MySQL database.

If you are tring to arbitrarily access a specific record or group of records in a MySQL database recordset, you might want to consider using the LIMIT clause of the SELECT statement to achieve this e.g. LIMIT 5,3 to return just the 6th,7th & 8th records - 3 records starting at index 5 (which is the 6th record).

down

fh at ez dot no ¶

19 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.

down

fh at ez dot no ¶

19 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.

down

Drew ¶

4 years ago


When using a PDOStatement with the fetch mode set to FETCH_CLASS, fetch will return false if no rows were found.

down

marcini ¶

17 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().

down

Black Knight ¶

8 years ago


this is just On reminder note about Second parameter -cursor_oriantation-

PDO::FETCH_ORI_NEXT :-
Fetch the next row in the result set. Valid only for scrollable cursors.

PDO::FETCH_ORI_PRIOR :-
Fetch the previous row in the result set. Valid only for scrollable cursors.

PDO::FETCH_ORI_FIRST :-
Fetch the first row in the result set. Valid only for scrollable cursors.

PDO::FETCH_ORI_LAST :-
Fetch the last row in the result set. Valid only for scrollable cursors.

PDO::FETCH_ORI_ABS :-
Fetch the requested row by row number from the result set. Valid only for scrollable cursors.

PDO::FETCH_ORI_REL :- 
Fetch the requested row by relative position from the current position of the cursor in the result set. Valid only for scrollable cursors.

down

lozitskiys at gmail dot com ¶

16 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; 

?>

down

-1

Alex ¶

13 years 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.

down

-1

josh ¶

16 years ago


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

down

-2

tastro ¶

10 years ago


Note that this way, the "fetch mode" will get "overwritten", and PDO::FETCH_PROPS_LATE won't be applied:

<?php
$sth = $db->prepare("SELECT * FROM user WHERE id = 1");
$sth->setFetchMode( PDO::FETCH_CLASS|PDO::FETCH_PROPS_LATE, 'user');
$sth->execute();
$user = $sth->fetch( PDO::FETCH_CLASS );
$sth->closeCursor();
?>

Instead, you should leave the parameter area for the fetch() method empty, like this (if you want to set the fetch mode with the setFetchMode() method):

<?php
$sth = $db->prepare("SELECT * FROM user WHERE id = 1");
$sth->setFetchMode( PDO::FETCH_CLASS|PDO::FETCH_PROPS_LATE, 'user');
$sth->execute();
$user = $sth->fetch();
$sth->closeCursor();
?>

down

-3

sumariva at gmail dot com ¶

12 years 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.

down

-2

aledmb at gmail dot com ¶

19 years ago


note that fetch constants are not included in the PDO class for PHP versions prior to 5.1

down

-4

tim at kooky dot org ¶

8 years ago


Be careful when using PDO::FETCH_LAZY.  It adds an additional field called queryString.  I'm not sure if this a bug or not. I'm using version 5.6.17 in Debian Jessie.

Query:  'select 1,2,3'

$row=$smt->fetch(PDO::FETCH_OBJ);
var_dump($row);

object(stdClass)#6 (3) {
  ["1"]=>
  string(1) "1"
  ["2"]=>
  string(1) "2"
  ["3"]=>
  string(1) "3"
}

$row=$smt->fetch(PDO::FETCH_LAZY);
var_dump($row);

object(PDORow)#3 (4) {
  ["queryString"]=>
  string(12) "select 1,2,3"
  ["1"]=>
  string(1) "1"
  ["2"]=>
  string(1) "2"
  ["3"]=>
  string(1) "3"
}

down

-6

avinoamr at gmail dot com ¶

18 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.

down

-16

Ome Ko ¶

13 years ago


Don't do 
if($objStatement->fetch()) return $objStatement->fetch(); 

You want   
if($blah=$objStatement->fetch()) return $blah;

Trust me on this one.

down

-14

BaBna ¶

17 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"; }
?>

down

-20

sumariva at gmail dot com ¶

11 years ago


I got problems during fetch of stored procedures with mssql following PDOException:

SQLSTATE[IMSSP]: The active result for the query contains no fields

with a a prepared statement like:
 EXEC [mydb].[stored_procedure_that_returns_select] ?;

The solution was to supress the count of records
SET NOCOUNT ON; EXEC [mydb].[stored_procedure_that_returns_select] ?;

Hope it helps!

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