sqlite_create_function

(PHP 5 < 5.4.0, sqlite >= 1.0.0)

Registers a "regular" User Defined Function for use in SQL statements

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

Object oriented style (method):

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

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.

Parameters:

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.

Returns:

No value is returned.

Examples:

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;
}
?>

Example of using the PHP function

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.

<?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