TAILIEUCHUNG - OBJECT-ORIENTED PHP Concepts, Techniques, and Code- P17

OBJECT-ORIENTED PHP Concepts, Techniques, and Code- P17:A number of years ago, before I started using PHP, I created dynamic web pages using C. This really wasn’t too different from some of the other options available at the time, though it seems almost unthinkable now. Creating a dynamic page meant outputting HTML from your script and recompiling that script if any changes needed to be made. | How It s Done In this application we take advantage of some of SQLite s advanced capabilities. Both triggers and views will be used. A trigger code that executes in response to an add edit or delete event will be used to mimic a datestamp field records will be automatically stamped whenever they are added or changed. Views are a convenient way of storing queries and can replace tables in the FROM clause of a SELECT statement. They can also be used with triggers so that updating a view updates the associated table. No database used in conjunction with PHP can escape comparison to MySQL. Where appropriate I will point out differences in SQL syntax between SQLite and MySQL. Likewise SQLite has a variety of different query methods. These will also be contrasted with MySQL functions. As you have seen throwing exceptions rather than trapping errors makes for cleaner code. SQLite has a built-in OO interface and there is an SQLiteException class. However only the SQLite database constructor throws exceptions. By extending the SQLite database class we can override the query methods so that a failed query also throws an exception. This derived class will also include data verification methods that make use of metadata extracted from the database. This will be done by querying the sqlite_master table and through the use of pragmas. A pragma modifies the way the SQLite library works but can also be used to query the database structure. We re only interested in the second use. A limited number of functions are available for use with SQLite s dialect of SQL. You ll see how this shortcoming can be overcome by creating user-defined functions UDFs . Getting Started SQLite comes bundled with PHP 5 so all you have to do to install the database is run the file. However if you do things this way you ll have to write code just to view your data or to examine the structure of your database. You might want to download the command-line version of SQLite instead. PHP 5

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