PDO::sqliteCreateFunction
(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
说明
public PDO::sqliteCreateFunction(
string $function_name
,
callable $callback
,
int $num_args
= -1,
int $flags
= 0):
bool
警告此函数是实验性的。此函数的表象,包括名称及其相关文档都可能在未来的
PHP 发布版本中未通知就被修改。使用本函数风险自担。
This method allows you to register a PHP function with SQLite as an
UDF (User Defined Function), so that it can be called
from within your SQL statements.
The UDF can be used in any SQL statement that can call functions, such as
SELECT and UPDATE statements and also in triggers.
参数
-
function_name
-
The name of the function used in SQL statements.
-
callback
-
Callback function to handle the defined SQL function.
注意:
Callback functions should return a type understood by SQLite (i.e.
scalar type).
This function need to be defined as:
-
value
-
The first argument passed to the SQL function.
-
values
-
Further arguments passed to the SQL function.
-
num_args
-
The number of arguments that the SQL function takes. If
this parameter is -1
, then the SQL function may take
any number of arguments.
-
flags
-
A bitwise conjunction of flags. Currently, only
PDO::SQLITE_DETERMINISTIC
is supported, which specifies
that the function always returns the same result given the same inputs
within a single SQL statement.
返回值
成功时返回 true
, 或者在失败时返回 false
。
示例
示例 #1 PDO::sqliteCreateFunction() example
<?php
function md5_and_reverse($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.