(PHP 8 >= 8.4.0)
Pdo\Sqlite::createFunction — Registers a user-defined function for use in SQL statements
$function_name,$callback,$num_args = -1,$flags = 0
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.
By using this method it is possible to override native SQL functions.
function_namecallback注意: Callback functions should return a type understood by SQLite (i.e. scalar type).
This function need to be defined as:
valueThe first argument passed to the SQL function.
valuesFurther arguments passed to the SQL function.
num_args-1,
then the SQL function may take any number of arguments.
flagsPdo\Sqlite::DETERMINISTIC is supported,
which specifies that the function always returns the same result given
the same inputs within a single SQL statement.
示例 #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();
?>