PDOStatement::fetch

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

PDOStatement::fetch — Fetches the next row from a result set

Descrizione

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

Fetches a row from a result set associated with a PDOStatement object. The mode parameter determines how PDO returns the row.

Elenco dei parametri

mode

Controls how the next row will be returned to the caller. This value must be one of the PDO::FETCH_* constants, defaulting to value of PDO::ATTR_DEFAULT_FETCH_MODE (which defaults to PDO::FETCH_BOTH).

PDO::FETCH_ASSOC: returns an array indexed by column name as returned in your result set
PDO::FETCH_BOTH (default): returns an array indexed by both column name and 0-indexed column number as returned in your result set
PDO::FETCH_BOUND: returns true and assigns the values of the columns in your result set to the PHP variables to which they were bound with the PDOStatement::bindColumn() method
PDO::FETCH_CLASS: returns a new instance of the requested class, mapping the columns of the result set to named properties in the class, and calling the constructor afterwards, unless PDO::FETCH_PROPS_LATE is also given. If mode includes PDO::FETCH_CLASSTYPE (e.g. PDO::FETCH_CLASS | PDO::FETCH_CLASSTYPE) then the name of the class is determined from a value of the first column.
PDO::FETCH_INTO: updates an existing instance of the requested class, mapping the columns of the result set to named properties in the class
PDO::FETCH_LAZY: combines PDO::FETCH_BOTH and PDO::FETCH_OBJ, and is returning a PDORow object which is creating the object property names as they are accessed.
PDO::FETCH_NAMED: returns an array with the same form as PDO::FETCH_ASSOC, except that if there are multiple columns with the same name, the value referred to by that key will be an array of all the values in the row that had that column name
PDO::FETCH_NUM: returns an array indexed by column number as returned in your result set, starting at column 0
PDO::FETCH_OBJ: returns an anonymous object with property names that correspond to the column names returned in your result set
PDO::FETCH_PROPS_LATE: when used with PDO::FETCH_CLASS, the constructor of the class is called before the properties are assigned from the respective column values.

cursorOrientation

For a PDOStatement object representing a scrollable cursor, this value determines which row will be returned to the caller. This value must be one of the PDO::FETCH_ORI_* constants, defaulting to PDO::FETCH_ORI_NEXT. To request a scrollable cursor for your PDOStatement object, you must set the PDO::ATTR_CURSOR attribute to PDO::CURSOR_SCROLL when you prepare the SQL statement with PDO::prepare().

cursorOffset

For a PDOStatement object representing a scrollable cursor for which the cursorOrientation parameter is set to PDO::FETCH_ORI_ABS, this value specifies the absolute number of the row in the result set that shall be fetched.

For a PDOStatement object representing a scrollable cursor for which the cursorOrientation parameter is set to PDO::FETCH_ORI_REL, this value specifies the row to fetch relative to the cursor position before PDOStatement::fetch() was called.

Valori restituiti

The return value of this function on success depends on the fetch type. In all cases, false is returned on failure or if there are no more rows.

Errori/Eccezioni

Emits an error with level E_WARNING if the attribute PDO::ATTR_ERRMODE is set to PDO::ERRMODE_WARNING.

Throws a PDOException if the attribute PDO::ATTR_ERRMODE is set to PDO::ERRMODE_EXCEPTION.

Esempi

Example #1 Fetching rows using different fetch styles

<?php
$sth = $dbh->prepare("SELECT name, colour FROM fruit");
$sth->execute();

/* Exercise PDOStatement::fetch styles */
print "PDO::FETCH_ASSOC: ";
print "Return next row as an array indexed by column name\n";
$result = $sth->fetch(PDO::FETCH_ASSOC);
print_r($result);
print "\n";

print "PDO::FETCH_BOTH: ";
print "Return next row as an array indexed by both column name and number\n";
$result = $sth->fetch(PDO::FETCH_BOTH);
print_r($result);
print "\n";

print "PDO::FETCH_LAZY: ";
print "Return next row as a PDORow object with column names as properties\n";
$result = $sth->fetch(PDO::FETCH_LAZY);
print_r($result);
print "\n";

print "PDO::FETCH_OBJ: ";
print "Return next row as an anonymous object with column names as properties\n";
$result = $sth->fetch(PDO::FETCH_OBJ);
print $result->name;
print "\n";
?>

Il precedente esempio visualizzerà:

PDO::FETCH_ASSOC: Return next row as an array indexed by column name
Array
(
    [name] => apple
    [colour] => red
)

PDO::FETCH_BOTH: Return next row as an array indexed by both column name and number
Array
(
    [name] => banana
    [0] => banana
    [colour] => yellow
    [1] => yellow
)

PDO::FETCH_LAZY: Return next row as a PDORow object with column names as properties
PDORow Object
(
    [name] => orange
    [colour] => orange
)

PDO::FETCH_OBJ: Return next row as an anonymous object with column names as properties
kiwi

Example #2 Fetching rows with a scrollable cursor

<?php
function readDataForwards($dbh) {
    $sql = 'SELECT hand, won, bet FROM mynumbers ORDER BY BET';
    $stmt = $dbh->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL));
    $stmt->execute();
    while ($row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_NEXT)) {
        $data = $row[0] . "\t" . $row[1] . "\t" . $row[2] . "\n";
        print $data;
    }
}
function readDataBackwards($dbh) {
    $sql = 'SELECT hand, won, bet FROM mynumbers ORDER BY bet';
    $stmt = $dbh->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL));
    $stmt->execute();
    $row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_LAST);
    do {
        $data = $row[0] . "\t" . $row[1] . "\t" . $row[2] . "\n";
        print $data;
    } while ($row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_PRIOR));
}

print "Reading forwards:\n";
readDataForwards($conn);

print "Reading backwards:\n";
readDataBackwards($conn);
?>

Il precedente esempio visualizzerà:

Reading forwards:
21    10    5
16    0     5
19    20    10

Reading backwards:
19    20    10
16    0     5
21    10    5

Example #3 Construction order

When objects are fetched via PDO::FETCH_CLASS the object properties are assigned first, and then the constructor of the class is invoked. If PDO::FETCH_PROPS_LATE is also given, this order is reversed, i.e. first the constructor is called, and afterwards the properties are assigned.

<?php
class Person
{
    private $name;

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

    public function tell()
    {
        if (isset($this->name)) {
            echo "I am {$this->name}.\n";
        } else {
            echo "I don't have a name yet.\n";
        }
    }
}

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

Il precedente esempio visualizzerà qualcosa simile a:

I am Alice.
I am Alice.
I don't have a name yet.
I am Bob.

Vedere anche:

PDO::prepare() - Prepares a statement for execution and returns a statement object
PDOStatement::execute() - Executes a prepared statement
PDOStatement::fetchAll() - Fetches the remaining rows from a result set
PDOStatement::fetchColumn() - Returns a single column from the next row of a result set
PDOStatement::fetchObject() - Fetches the next row and returns it as an object
PDOStatement::setFetchMode() - Set the default fetch mode for this statement

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User Contributed Notes 22 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 ¶

10 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

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

public at grik dot net ¶

13 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

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 ¶

18 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

fh at ez dot no ¶

18 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

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

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

-2

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

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

-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

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

-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"
}

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