PHP - Manual: sqlite_create_function

2024-11-15

sqlite_create_function

SQLiteDatabase::createFunction

(PHP 5 < 5.4.0, sqlite >= 1.0.0)

sqlite_create_function -- SQLiteDatabase::createFunction — Registers a "regular" User Defined Function for use in SQL statements

说明

sqlite_create_function ( resource $dbhandle , string $function_name , callable $callback [, int $num_args = -1 ] ) : void

面向对象风格 (method):

public SQLiteDatabase::createFunction ( string $function_name , callable $callback [, int $num_args = -1 ] ) : void

sqlite_create_function() 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

dbhandle: The SQLite Database resource; returned from sqlite_open() when used procedurally. This parameter is not required when using the object-oriented method.
function_name: The name of the function used in SQL statements.
callback: Callback function to handle the defined SQL function.

Note: 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.

Note: 为兼容其他数据库扩展(比如 MySQL)，支持两种可替代的语法。推荐第一种格式，函数的第一个参数是dbhandle。

返回值

没有返回值。

范例

Example #1 sqlite_create_function() example


<?php
function md5_and_reverse($string) 
{
    return strrev(md5($string));
}

if ($dbhandle = sqlite_open('mysqlitedb', 0666, $sqliteerror)) {
    
    sqlite_create_function($dbhandle, 'md5rev', 'md5_and_reverse', 1);
    
    $sql  = 'SELECT md5rev(filename) FROM files';
    $rows = sqlite_array_query($dbhandle, $sql);
} else {
    echo 'Error opening sqlite db: ' . $sqliteerror;
    exit;
}
?>

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.

PHP registers a special function named php when the database is first opened. The php function can be used to call any PHP function without having to register it first.

Example #2 Example of using the PHP function


<?php
$rows = sqlite_array_query($dbhandle, "SELECT php('md5', filename) from files");
?>

This example will call the md5() on each filename column in the database and return the result into $rows

Note:
For performance reasons, PHP will not automatically encode/decode binary data passed to and from your UDF's. You need to manually encode/decode the parameters and return values if you need to process binary data in this way. Take a look at sqlite_udf_encode_binary() and sqlite_udf_decode_binary() for more details.

Tip

It is not recommended to use UDF's to handle processing of binary data, unless high performance is not a key requirement of your application.

Tip

You can use sqlite_create_function() and sqlite_create_aggregate() to override SQLite native SQL functions.

参见

sqlite_create_aggregate() - Register an aggregating UDF for use in SQL statements

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User Contributed Notes 4 notes

down

anrdaemon at freemail dot ru ¶

2 years ago


The (probably) all too often requested regexp() function actually works just fine.

<?php

$db = new PDO('sqlite::memory:', null, null, [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);

$db->sqliteCreateFunction('regexp', function($y, $x) { return preg_match('/' . addcslashes($y, '/') . '/', $x); }, 2);

$db->query('SELECT ("Things!" REGEXP "^T") `result`');

?>

down

Dodolidet ¶

7 years ago


Although you can create an UDF named 'regexp()', I think it won't be registered as REGEXP operator..

<?php
//registering REGEXP
function my_sqlite_regexp($x,$y){
    return (int)preg_match("`$y`i",$x);
}
echo $db->createFunction('regexp','my_sqlite_regexp',2);

//testing regexp as function, working
$res = $db->query("SELECT * FROM x WHERE regexp(c,'h')", SQLITE_ASSOC , $err) ;

//testing regexp as operator, not working, near "REGEXP": syntax error
$res = $db->query("SELECT * FROM x WHERE c REGEXP 'h'", SQLITE_ASSOC , $err); 
?>

I'd also swapped the function parameters $x and $y, but also not works..
-----
From SQLite documentation:
"The REGEXP operator is a special syntax for the regexp() user function. No regexp() user function is defined by default and so use of the REGEXP operator will normally result in an error message. If a application-defined SQL function named "regexp" is added at run-time, that function will be called in order to implement the REGEXP operator."

down

info at myphp dot it ¶

14 years ago


The function can be a method of a class:

<?php

class sqlite_function {

    function md5($value)
    {
        return md5($value);
    }

}

$dbhandle = sqlite_open('SQLiteDB');

sqlite_create_function($dbhandle, 'md5', array('sqlite_function', 'md5'), 1);

// From now on, you can use md5 function inside your SQL statements

?>

It works fine :)

down

Brett ¶

14 years ago


In my previous comment, there was an error in the code which was causing the issue.

Removing the surrounding quotes from from_unixtime()'s return value solved the issue, and so UDFs _do work_ from within DELETEs and INSERTs!  Yay!

<?php

// SQLite UDF
// Mimic MySQL FROM_UNIXTIME
function from_unixtime($unixtime)
{
    return date('Y-m-d H:i:s', $unixtime);  // no surrouding quotes
}

?>

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官方地址：https://www.php.net/manual/en/function.sqlite-create-function.php

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PHP官方手册 - 互联网笔记

sqlite_create_function

SQLiteDatabase::createFunction

说明

参数

返回值

范例

参见

User Contributed Notes 4 notes