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
Description
$dbhandle
, string $function_name
, callable $callback
[, int $num_args = -1
] )Object oriented style (method):
$function_name
, callable $callback
[, int $num_args = -1
] )sqlite_create_function() allows you to register a PHP function with SQLite as an UDF (User Defined Function), so that it can be called from within your SQL statements.
The UDF can be used in any SQL statement that can call functions, such as SELECT and UPDATE statements and also in triggers.
Parameters
-
dbhandle -
The SQLite Database resource; returned from sqlite_open() when used procedurally. This parameter is not required when using the object-oriented method.
-
function_name -
The name of the function used in SQL statements.
-
callback -
Callback function to handle the defined SQL function.
Note: Callback functions should return a type understood by SQLite (i.e. scalar type).
-
num_args -
Hint to the SQLite parser if the callback function accepts a predetermined number of arguments.
Note: Two alternative syntaxes are supported for compatibility with other database extensions (such as MySQL). The preferred form is the first, where the
dbhandleparameter is the first parameter to the function.
Return Values
No value is returned.
Examples
Example #1 sqlite_create_function() example
<?php
function md5_and_reverse($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 $rows
Note:
For performance reasons, PHP will not automatically encode/decode binary data passed to and from your UDF's. You need to manually encode/decode the parameters and return values if you need to process binary data in this way. Take a look at sqlite_udf_encode_binary() and sqlite_udf_decode_binary() for more details.
It is not recommended to use UDF's to handle processing of binary data, unless high performance is not a key requirement of your application.
You can use sqlite_create_function() and sqlite_create_aggregate() to override SQLite native SQL functions.
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Коментарии
The function can be a method of a class:
<?php
class sqlite_function {
function md5($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 :)
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', $unixtime); // no surrouding quotes
}
?>
Although you can create an UDF named 'regexp()', I think it won't be registered as REGEXP operator..
<?php
//registering REGEXP
function my_sqlite_regexp($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."
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`');
?>