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PDO::sqliteCreateFunction

(no version information, might be only in CVS)

PDO::sqliteCreateFunction --  Registers a User Defined Function for use in SQL statements

說明

bool PDO::sqliteCreateFunction ( string function_name, callback callback [, int num_args] )

警示

本函數是實驗性的。本函數的行為，內含函數名稱以及其它任何關於本函數的文件可能會在沒有知會的情況下隨 PHP 以後的發佈而改變。使用本函數風險自擔。

PDO::sqliteCreateFunction() 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.

參數

function_name

The name of the function used in SQL statements.

callback

Callback function to handle the defined SQL function.

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

num_args

Hint to the SQLite parser if the callback function accepts a predetermined number of arguments.

注: 為相容其它資料庫（例如 MySQL），支援另兩種替代的語法。推薦用第一種，dbhandle 參數作為函數的第一個參數。

範例

例子 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.

提示: You can use PDO::sqliteCreateFunction() and PDO::sqliteCreateAggregate() to override SQLite native SQL functions.

注: This method is not available with the SQLite2 driver. Use the old style sqlite API for that instead.

參見

PDO::sqliteCreateAggregate()
sqlite_create_function()
sqlite_create_aggregate()



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PDO::sqliteCreateAggregate上一級Secure Shell2 Functions