PHP AND DATABASES IN MYSQL

Prof. Assoc. Lule Ahmedi Course: Internet Programming

Web Database Architecture

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

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

Some DBMS Systems to Connect To

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)

Running Example: Bookstore Catalog

Running Example: Bookstore Catalog

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

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

Choosing a Database to Use

Querying the Database

Retrieving the Query Results

- serves to encode characters with

special meanings in HTML, like ’&’, ’<’, ’>’, ’"’, etc.

Disconnecting From the Database

Inserting Data Into the Database

Inserting Data Into the Database (cont.)

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

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

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:

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:

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