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Pdo\Sqlite::createFunction

(PHP 8 >= 8.4.0)

Pdo\Sqlite::createFunction — Registers a user-defined function for use in SQL statements

Опис

public Pdo\Sqlite::createFunction(
    string $function_name,
    callable $callback,
    int $num_args = -1,
    int $flags = 0
): bool

This method allows PHP function to be registered with SQLite as a user-defined function, so that it can be called within SQL queries. The defined function can be used in any SQL query that allows function calls, for example SELECT, UPDATE, or triggers.

Підказка

By using this method it is possible to override native SQL functions.

Параметри

function_name
The name of the function used in SQL statements.
callback
Callback function to handle the defined SQL function.

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

This function need to be defined as:

callback(mixed $value, mixed ...$values): mixed
value

The first argument passed to the SQL function.

values

Further arguments passed to the SQL function.

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 bitmask 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.

Значення, що повертаються

Повертає true у разі успіху або false в разі помилки.

Приклади

Приклад #1 Pdo\Sqlite::createFunction() example

In this example, we have a function that calculates the SHA256 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 there is no need to process the result using a foreach loop after the query.

<?php
function sha256_and_reverse($string)
{
return strrev(hash('sha256', $string));
}

$db = new Pdo\Sqlite('sqlite::sqlitedb');
$db->sqliteCreateFunction('sha256rev', 'sha256_and_reverse', 1);
$rows = $db->query('SELECT sha256rev(filename) FROM files')->fetchAll();
?>

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