PDO::sqliteCreateFunction
(PHP 5 >= 5.1.0, PHP 7, PECL pdo_sqlite >= 1.0.0)
PDO::sqliteCreateFunction — Registers a User Defined Function for use in SQL statements
Description
$function_name
, callable $callback
[, int $num_args = -1
[, int $flags = 0
]] ) : boolThis function is EXPERIMENTAL. The behaviour of this function, its name, and surrounding documentation may change without notice in a future release of PHP. This function should be used at your own risk.
This method allows you to register a PHP function with SQLite as an UDF (User Defined Function), so that it can be called from within your SQL statements.
The UDF can be used in any SQL statement that can call functions, such as SELECT and UPDATE statements and also in triggers.
Parameters
-
function_name -
The name of the function used in SQL statements.
-
callback -
Callback function to handle the defined SQL function.
Note: Callback functions should return a type understood by SQLite (i.e. scalar type).
This function need to be defined as:
-
value1 -
The first argument passed to the SQL function.
-
... -
Further arguments passed to the SQL function.
-
-
num_args -
The number of arguments that the SQL function takes. If this parameter is -1, then the SQL function may take any number of arguments.
-
flags -
A bitwise conjunction of flags. Currently, only
PDO::SQLITE_DETERMINISTICis supported, which specifies that the function always returns the same result given the same inputs within a single SQL statement.
Examples
Example #1 PDO::sqliteCreateFunction() example
<?php
function md5_and_reverse($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.
You can use PDO::sqliteCreateFunction and PDO::sqliteCreateAggregate to override SQLite native SQL functions.
Note:
This method is not available with the SQLite2 driver. Use the old style sqlite API for that instead.
See Also
- PDO::sqliteCreateAggregate
- sqlite_create_function() - Registers a "regular" User Defined Function for use in SQL statements
- sqlite_create_aggregate() - Register an aggregating UDF for use in SQL statements
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Document created the 30/01/2003, last modified the 26/10/2018
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References
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