SQLite (PDO)
PHP-Handbuch

PDO::sqliteCreateFunction

Registers a User Defined Function for use in SQL statements

Beschreibung

public bool PDO::sqliteCreateFunction ( string $function_name , callable $callback [, int $num_args = -1 [, int $flags = 0 ]] )
Warnung

Diese Funktion ist EXPERIMENTELL. Das Verhalten, der Funktionsname und alles Andere, was hier dokumentiert ist, kann sich in zukünftigen PHP-Versionen ohne Ankündigung ändern. Seien Sie gewarnt und verwenden Sie diese Funktion auf eigenes Risiko.

This method allows you to register a PHP function with SQLite as an UDF (User Defined Function), so that it can be called from within your SQL statements.

The UDF can be used in any SQL statement that can call functions, such as SELECT and UPDATE statements and also in triggers.

Parameter-Liste

function_name

The name of the function used in SQL statements.

callback

Callback function to handle the defined SQL function.

Hinweis: Callback functions should return a type understood by SQLite (i.e. scalar type).

num_args

The number of arguments that the SQL function takes. If this parameter is -1, then the SQL function may take any number of arguments.

flags

A bitwise conjunction of flags. Currently, only PDO::SQLITE_DETERMINISTIC is supported, which specifies that the function always returns the same result given the same inputs within a single SQL statement.

Rückgabewerte

Gibt bei Erfolg TRUE zurück. Im Fehlerfall wird FALSE zurückgegeben.

Changelog

Version Beschreibung
PHP 7.1.4 The flags has been added.

Beispiele

Beispiel #1 PDO::sqliteCreateFunction example

<?php
function md5_and_reverse($string) 
{
    return strrev(md5($string));
}

$db = new PDO('sqlite:sqlitedb');
$db->sqliteCreateFunction('md5rev', 'md5_and_reverse', 1);
$rows = $db->query('SELECT md5rev(filename) FROM files')->fetchAll();
?>

In this example, we have a function that calculates the md5 sum of a string, and then reverses it. When the SQL statement executes, it returns the value of the filename transformed by our function. The data returned in $rows contains the processed result.

The beauty of this technique is that you do not need to process the result using a foreach loop after you have queried for the data.

Tipp

You can use PDO::sqliteCreateFunction and PDO::sqliteCreateAggregate to override SQLite native SQL functions.

Hinweis:

This method is not available with the SQLite2 driver. Use the old style sqlite API for that instead.

Siehe auch