Description
bool
sqlite_create_function ( resource dbhandle, string function_name, mixed callback [, int num_args])
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.
dbhandle specifies the database handle that you
wish to extend, function_name specifies the name
of the function that you will use in your SQL statements,
callback is any valid PHP callback to specify a
PHP function that should be called to handle the SQL function.
The optional parameter num_args is used as a hint
by the SQLite expression parser/evaluator. It is recommended that you
specify a value if your function will only ever accept a fixed number of
parameters.
The UDF can be used in any SQL statement that can call functions, such as
SELECT and UPDATE statements and also in triggers.
Ejemplo 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.
Ejemplo 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
|
Nota:
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.
Sugerencia:
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.
See also sqlite_create_aggregate().
