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PHP5中文手册
sqlite_create_functionSQLiteDatabase->createFunction(No version information available, might be only in CVS) SQLiteDatabase->createFunction — Registers a "regular" User Defined Function for use in SQL statements 说明
void sqlite_create_function
( resource $dbhandle
, string $function_name
, callback $callback
[, int $num_args
] )
Object oriented style (method): SQLiteDatabase
void createFunction
( string $function_name
, callback $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. The UDF can be used in any SQL statement that can call functions, such as SELECT and UPDATE statements and also in triggers. 参数
返回值无返回值。 范例
Example#1 sqlite_create_function() example
<?php 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 This example will call the md5() on each filename column in the database and return the result into $rows
Tip
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. Tip
You can use sqlite_create_function() and sqlite_create_aggregate() to override SQLite native SQL functions. |