Chapter 4 Files and Database handling

 - What is a DSN?

DSN stands for Data Source Name. It is a string that specifies a database connection, typically used in database-related operations.

-How to delete file in PHP?

The unlink() function is used to delete a file in PHP. For example:

$fileToDelete = 'example.txt';

unlink($fileToDelete);

 -Write a PHP script accept and insert records in employee table.

<?php

// Assuming database connection is established

$employeeName = $_POST['employeeName'];

$employeeAge = $_POST['employeeAge'];

$employeeSalary = $_POST['employeeSalary'];

$sql = "INSERT INTO employee (name, age, salary) VALUES ('$employeeName', $employeeAge, $employeeSalary)";

// Execute the SQL query to insert records

mysqli_query($conn, $sql);

// Close the database connection

mysqli_close($conn);

?>

-What are the different placeholders used in SQL query?

? (Question Mark):

Used as a parameter placeholder in prepared statements.

:name (Colon Name):

Named placeholders in prepared statements, commonly used in PDO.

$1, $2, ... (Dollar Sign):

Parameter placeholders in PostgreSQL.

- Write steps to create connection with Postgre SQL database and display

 the data.

Install PostgreSQL Extension:

Ensure that the PostgreSQL extension is installed and enabled in PHP.

Create Database Connection:

Use pg_connect or PDO to establish a connection to the PostgreSQL database.

Execute Queries:

Use pg_query or other relevant functions to execute SQL queries.

-Consider the following relational data base

 Movie (Movie - no , Movie - name, year)

 Actor (Actor - no, Actor - name, Movie - no)

<?php

// Assuming database connection is established

$movieName = $_POST['movieName'];

$sql = "SELECT Actor_name FROM Actor WHERE Movie_name = '$movieName'";

$result = mysqli_query($conn, $sql);

while ($row = mysqli_fetch_assoc($result)) {

    echo $row['Actor_name'] . "<br>";

}

// Close the database connection

mysqli_close($conn);

?>

 -State the advantage of using PEAR DB functions.
The PEAR DB library provides a database abstraction layer, making it easier to switch between different database systems without changing the code. It promotes portability and helps in maintaining a consistent interface for database operations.

-Consider a table student (rno, name, class). Assume database

 stud already exists. Write a PHP script to accept a student

 roll no. and display details of that student using PEAR DB

 functions.

<?php

// Assuming database connection is established using PEAR DB

$rollNo = $_POST['rollNo'];

// Execute a query to fetch student details based on roll number

// Use PEAR DB functions like db_query, etc.

// Display student details

echo "Student Roll No: $rollNo";

// Display other details fetched from the database

?>

-Explain prepare ( ) and execute ( ) command in database handling

In PHP database handling with PDO, prepare() is used to prepare an SQL statement, and execute() is used to execute that prepared statement.

 -Accept directory name from user. Write PHP program to change current

 directory to accepted directory name and count number of files and directories in it

$dir = "/path/to/directory";

chdir($dir);

$files = scandir($dir);

$numFiles = count($files) - 2;  // Subtracting . and .. from the count

echo "Number of files and directories: $numFiles";

-Write a PHP script to accept a file name from user and

 display last access date and time of a file.

<?php

$filename = 'example.txt';

// Display last access date and time

echo "Last access time: " . date("F d Y H:i:s.", fileatime($filename));

?>

 

- State the pear db function to get system error message, if

 the database connection fails.

 -How to get the user ID of the owner of the specified

 file ?

 -Assume database empdb is already exists. Write a PHP script

 using postgreSQL to increment salary of all employees by 10%.

- Consider table emp(eno, ename, salary).

-Write a PHP script to display date and time of a file when

 it was last accessed.

-Explain DB :: connect( )

- Which operator is used to compare data as well as data type ?

-What is purpose of file)?

- Write connect function in PEAR DB for pestgreSQL How to release connection in database specifir way?

- Write stope to seept database using database specific way.

-Write a PHP program to add aasigronment record of the given student. Consider-heo, name, assignment, set, question eo, marks, date accept from student).

-What is Data type List different Data types in PHP? Explain

-What are the different class methods and object methods available in PRAR DB ibrary? Kaplain.

- Write purpose of resource data type with suitable example.