Pdo\Sqlite::createFunction
Registers a user-defined function for use in SQL statements
説明
public bool Pdo\Sqlite::createFunction(
string $function_name,
callable $callback,
int $num_args = -1,
int $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.
ヒント
By using this method it is possible to override native SQL functions.
パラメータ
-
function_name
-
The name of the function used in SQL statements.
-
callback
-
Callback function to handle the defined SQL function.
注意:
Callback functions should return a type understood by SQLite (i.e.
scalar type).
This function need to be defined as:
mixed callback(mixed $value, mixed ...$values)
-
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.
戻り値
成功した場合に true を、失敗した場合に false を返します。
例
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();
?>
参考
- Pdo\Sqlite::createAggregate
- Pdo\Sqlite::createCollation
- sqlite_create_function
- sqlite_create_aggregate