PHP AND DATABASES IN MYSQL. Prof. Assoc. Lule Ahmedi Course: Internet Programming

Transcription

1 PHP AND DATABASES IN MYSQL Prof. Assoc. Lule Ahmedi Course: Internet Programming

2 Web Database Architecture

3 Server-Side vs. Client-Side Execution When linking databases and Web pages, most of time Server-side code Embedded code with server-side execution Why not client-side execution? Clients are usually too far away Servers should not trust the clients Servers are designated to serve applications that might well require a lot more horsepower Disadvantage: Server might be overloaded while clients sit idle

4 PHP Database APIs Several API styles in PHP of connecting to a DB a) According to programming paradigm: Procedural database APIs Deprecated mysql extension mysqli improved extension, its procedural version Object-oriented database APIs PDOs (PHP Data Objects) mysqli improved extension, its object-oriented version PEAR::DB (written in PHP, not in C) b) According to abstraction level to vendor databases: Vendor-specific database APIs mysql and mysqli extensions for MySQL, OCI8 for Oracle, etc. Abstraction layer APIs (generic database APIs, i.e., vendor-neutral) PDO PEAR::DB ODBC drivers approach

5 Some DBMS Systems to Connect To

6 Vendor-Specific vs Generic APIs Tradeoff required selecting between these two approaches Vendor-specific APIs (mysql, mysqli,..) Pros: Complete functionality of a certain vendor db (say MySQL, or Oracle, or Microsoft SQL, or DB2 IBM, or..) covered Cons: Extension to support other vendor db-s (say MySQL, or Oracle, or Microsoft SQL, or DB2 IBM, or..) incurs additional development costs + learning new syntax Generic APIs (PDO, PEAR::DB, ODBC) Pros: Extension to other vendor db-s almost at no cost Cons: Functionality of a certain vendor db incompletely covered due to generalization (common layer)

7 Running Example: Bookstore Catalog

8 Running Example: Bookstore Catalog

9 Checking and Filtering Input Data - is used to strip any whitespace - is checked although it comes from an HTML - sensible screen data - when submitting user input to a database - when returning data from a database

10 Setting Up a Connection Nonpersistent connection Closes when a script finishes execution, or through the function call Since limited # of connections can exist at the same time Persistent connections Lives longer than the script itself To save connection/disconnection time and server overhead In original deprecated version as

11 Choosing a Database to Use

12 Querying the Database

13 Retrieving the Query Results - serves to encode characters with special meanings in HTML, like &, <, >, ", etc.

14 Disconnecting From the Database

15 Inserting Data Into the Database

16 Inserting Data Into the Database (cont.)

17 Other Useful PHP MySQL Functions (cont.) Freeing up resources: Example: Creating databases: Working with transactions: See php.net for a complete list of mysqli functions

18 Other PHP Database APIs A set of certain extension libraries available in PHP to connect to a specific vendor database: OCI8 for Oracle mssql for Microsoft SQL PostgreSQL IBM DB2 Informix Sybase MongoDB SQLite They all share common principles of connecting and querying Differ slightly on functionality If there is no support, i.e. no specific library available in PHP for a given database, use the generic ODBC functions Open Database Connectivity - a standard for connections to databases Limited functionality due to being designated to work with everything

19 Generic Database API: PEAR DB Object-oriented Offers database abstraction classes such as Metabase or PEAR::DB PEAR::DB abstraction layer is the core component of PEAR Vendor-neutral common abstraction layer Same function names for each different type of database Difference is basically syntactic, e.g., To connect: where To retrieve result rows:

20 Generic Database API: PDO PDO stands for PHP Data Objects Object-oriented Vendor-neutral common abstraction layer Same function names for each different type of database Difference is basically syntactic, e.g., To connect: To retrieve result rows:

21 References [1] PHP and MySQL Web Development (4th Edition). Luke Welling, Laura Thompson. Addison-Wesley Professional, 2014 [2] Fundamentals of Web Development. Randy Connolly, Ricardo Hoar. Pearson, 2014 php.net