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PDO->sqliteCreateFunction()
Registers a User Defined Function for use in SQL statements
()
PDO {
bool sqliteCreateFunction(string function_name,
callback callback,
int num_args);
}This function is EXPERIMENTAL. The behaviour of this function, the name of this function, and anything else documented about this function may change without notice in a future release of PHP. Use this function 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).
- num_args
Hint to the SQLite parser if the callback function accepts a predetermined number of arguments.
Examples
Example 2342. 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.
This method is not available with the SQLite2 driver. Use the old style sqlite API for that instead.