IGNOU BCA MCA Students - VIVA Question Answer for PHP Part VII

IGNOU BCA MCA Students - VIVA Question Answer for PHP

PHP Selected Question Answer - PART VII

1.  Distinguish between urlencode and urldecode?

This method is best when encode a string to used in a query part of a url. it returns a string in which all non-alphanumeric characters except -_. have replece with a percentege(%) sign . the urldecode->Decodes url to encode string as any %and other symbole are decode by the use of the urldecode() function.

2.  What are the different errors in PHP?

In PHP, there are three types of runtime errors, they are:

Warnings: 

These are important errors. Example: When we try to include () file which is not available. These errors are showed to the user by default but they will not result in ending the script. 

Notices: 

These errors are non-critical and trivial errors that come across while executing the script in PHP. Example: trying to gain access the variable which is not defined. These errors are not showed to the users by default even if the default behavior is changed. 

Fatal errors: 

These are critical errors. Example: instantiating an object of a class which does not exist or a non-existent function is called. These errors results in termination of the script immediately and default behavior of PHP is shown to them when they take place. Twelve different error types are used to represent these variations internally.

3.  Database connection example

Before you can get content out of your MySQL database, you must know how to establish a connection to MySQL from inside a PHP script. To perform basic queries from within MySQL is very easy. This article will show you how to get up and running.

Let's get started. The first thing to do is connect to the database.The function to connect to MySQL is called mysql_connect. This function returns a resource which is a pointer to the database connection. It's also called a database handle, and we'll use it in later functions. Don't forget to replace your connection details.

<?php $username = "your_name"; $password = "your_password"; $hostname = "localhost";  //connection to the database $dbhandle = mysql_connect($hostname, $username, $password)    or die("Unable to connect to MySQL"); echo "Connected to MySQL<br>"; ?>

All going well, you should see "Connected to MySQL" when you run this script. If you can't connect to the server, make sure your password, username and hostname are correct.

Once you've connected, you're going to want to select a database to work with. Let's assume the database is called 'examples'. To start working in this database, you'll need the mysql_select_db() function:

<?php //select a database to work with $selected = mysql_select_db("examples",$dbhandle)    or die("Could not select examples"); ?>

Now that you're connected, let's try and run some queries. The function used to perform queries is named - mysql_query(). The function returns a resource that contains the results of the query, called the result set. To examine the result we're going to use the mysql_fetch_array function, which returns the results row by row. In the case of a query that doesn't return results, the resource that the function returns is simply a value true or false.

A convenient way to access all the rows is with a while loop. Let's add the code to our script:

<?php //execute the SQL query and return records $result = mysql_query("SELECT id, model, year FROM cars"); //fetch tha data from the database while ($row = mysql_fetch_array($result)) {    echo "ID:".$row{'id'}." Name:".$row{'model'}."     ".$row{'year'}."<br>"; } ?>

Finally, we close the connection. Although this isn't strictly speaking necessary, PHP will automatically close the connection when the script ends, you should get into the habit of closing what you open.

<?php //close the connection mysql_close($dbhandle); ?>

Here is a code in full:

<?php $username = "your_name"; $password = "your_password"; $hostname = "localhost";  //connection to the database $dbhandle = mysql_connect($hostname, $username, $password)   or die("Unable to connect to MySQL"); echo "Connected to MySQL<br>"; //select a database to work with $selected = mysql_select_db("examples",$dbhandle)    or die("Could not select examples"); //execute the SQL query and return records $result = mysql_query("SELECT id, model,year FROM cars"); //fetch tha data from the database  while ($row = mysql_fetch_array($result)) {    echo "ID:".$row{'id'}." Name:".$row{'model'}."Year: ". //display the results    $row{'year'}."<br>"; } //close the connection mysql_close($dbhandle); ?>

To create 'examples' database on your MySQL server you should run the following script:

CREATE DATABASE `examples`; USE `examples`; CREATE TABLE `cars` (    `id` int UNIQUE NOT NULL,    `name` varchar(40),    `year` varchar(50),    PRIMARY KEY(id) ); INSERT INTO cars VALUES(1,'Mercedes','2000'); INSERT INTO cars VALUES(2,'BMW','2004'); INSERT INTO cars VALUES(3,'Audi','2001');