Internet Information Systems Writing to Databases and Amending Data

Objectives Review Inserting data Cleaning data Redirects/Receipts Server-side validation Amending and deleting data Issues in writing data

Review Create tables & display data DEMO phpMyAdmin, filmscript Viewfilm.php Querying data -DEMO examples Demo cat_products.php As well as reading data, also need to Insert, Amend and Delete Uses - Shopping carts, personalisation,

Data Insertion – Phases Client: Data collection Web Form + Client-side validation Server: Check Data Submitted & Clean Check data arrived Check for dodgy characters. Data Validation Data is in correct format for entry into database. Insert/Amend the data

Data Submitted Demo AddAnimal.php <?php $country = $_GET['country']; $animal = $_GET['animal']; // If no user input, then present Form if (empty($animal) || empty($country)) { //Error – go back to form} Could use empty function if (empty($animal) || empty($country)) Demo Create User isset function to see if form is submitted

Cleaning Data Avoid bad characters = ‘ “” \ nulls Magic quotes - all escaped with a backslash automatically Set on server mysql_real_escape_string($somestring); Clean white space at beginning or end. Trim $newuser = trim($newuser);

Reloading Data Problem http is ‘Stateless’ => ‘reload’ problem with inserts/updates. Submit details – then Refresh Variables & values are resubmitted Can avoid with redirection -> receipt? http Location:header CreateUserWithReceipt if (record added) header("Location: userReceipt.php?status=T“); else header("Location: userReceipt.php? status=F“)

Server-Side Validation Must ensure data is in correct format for database – validation by: Database or Server-Side scripts Database Could php mysql_error() function to trap errors returned from DB Server-Side Scripts Submit form – then check fields Can use regular expressions int ereg ( string pattern, string string [, array &regs] )

Regular Expressions PHP Functions ereg() and eregi() int ereg ( string pattern, string string [, array &regs] ) $String = “Course Technology” ereg(“course technology”, $String) //returns false ereg(“Course Technology”, $String) //returns false eregi(“course technology”, $String) //returns false You can see these functions would be useful in searches ^ means start of a string $ means the end of a string [0-9] means there must be a digit from 0 – 9 {4} means there must be 4 in quantity Demo – CustomerDetailsError.php ereg("^([0-9]{2})/([0-9]{2})/([0-9]{4})$", $dob, $parts))

Database Updates and Deletes Update - usually 3 stages 1. Using key value - matching data is read from the database 2. The data is presented for modification 3. The data is updated using the key value from the first step. Demo - CustUpdateInsert $query = "UPDATE customer SET surname = '$surname', ……

Example - Delete 1. Identify row or rows to be deleted 2. Remove data with SQL DELETE Demo DeleteAnimal – getting ID $query = "DELETE FROM symbols WHERE id = ".$_GET['id']; mysql_affected_rows() Demo Cust_delete

Writing To Databases - Issues Multiple users – simultaneous insertion, deletion and updating Unrepeatable reads (stock, planes) Transactions – viable and complete Concurrency – same row being altered Locking mechanisms provided by mySQL

Summary Reviewed Create tables in MySQL View and Query data Collect, clean, validate data before inserting or amending Validation (searching) using regular expressions Avoid ‘Reload’ problem with redirect Updates and Deletes