(PHP 5 >= 5.1.0, PHP 7, PHP 8, PECL pdo_sqlite >= 1.0.0)
PDO::sqliteCreateFunction — Registers a User Defined Function for use in SQL statements
$function_name,$callback,$num_args = -1,$flags = 0此函数是实验性的。此函数的表象，包括名称及其相关文档都可能在未来的 PHP 发布版本中未通知就被修改。使用本函数风险自担。
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.
function_nameThe name of the function used in SQL statements.
callbackCallback 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:
valueThe first argument passed to the SQL function.
valuesFurther 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 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.
| 版本 | 说明 |
|---|---|
| 7.1.4 |
The flags parameter has been added.
|
示例 #1 PDO::sqliteCreateFunction() example
<?php
function md5_and_reverse($string)
{
return strrev(hash('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.
You can use PDO::sqliteCreateFunction and PDO::sqliteCreateAggregate to override SQLite native SQL functions.