PHP File Handling & MySQL Basics: Short & Long Q&A

  

PHP file handling & MySQL

Very Short Answers 

1.   What is file_put_contents() function?

file_put_contents() writes a string to a file. If the file exists, it overwrites it. If it doesn’t exist, it creates the file and writes content to it.

2.   Define unlink() function?

The unlink() function deletes a file from the system. It takes the filename as a parameter. If the file exists, it is removed; otherwise, it returns false.

3.   Discuss feof() function?

feof() checks if the end of a file has been reached during reading. It returns true if the file pointer is at the end of the file, else false.

4.   What is MySQL?

MySQL is a free, open-source relational database management system. It is used to store and manage data using structured query language (SQL) and is often used with PHP.

5.   What is ODBC?

ODBC (Open Database Connectivity) is a standard API that allows applications to connect and interact with different database systems using a common set of commands and functions.

 

  Short Answers

1.   What is file handling in PHP?

File handling in PHP refers to reading, writing, and manipulating files. PHP provides functions like fopen(), fread(), fwrite(), and fclose() to work with files. It is used for storing data, logs, or generating reports without using databases.

2.   Explain fwrite() function in PHP?

The fwrite() function in PHP is used to write data to a file. It requires a file pointer and the string to write. The file must be opened using fopen() in write, append, or update mode before using fwrite().

3.   What is include() function?

include() is used to insert the content of one PHP file into another. It is useful for reusing code like headers and footers. If the file doesn’t exist, a warning is shown, and script continues.

4.   Explain require() function?

require() includes a PHP file like include(), but if the file is missing, it causes a fatal error and stops the script. It is used for essential files like database connection or config files.

5.   Syntax to create a table? CREATE TABLE students (

  id INT PRIMARY KEY AUTO_INCREMENT,   name VARCHAR(50),   age INT

);

This command creates a table named students with three fields: id, name, and age.

 

  Long Answers 

1.   How will you open a file in different modes? In PHP, files are opened using the fopen() function. It requires two parameters: the filename and the mode.

The mode determines how the file will be handled. Common file modes are:

•        'r': Open for reading. File must exist.

•        'r+': Open for reading and writing. File must exist.

•        'w': Open for writing. Creates a new file or truncates existing one.

•        'w+': Open for reading and writing. Truncates existing file or creates new.

•        'a': Open for appending. Creates file if it doesn’t exist.

•        'a+': Read and append mode.

•        'x': Create a new file. Error if file exists.

•        'x+': Create and open file for reading and writing.

Example:

$file = fopen("data.txt", "r");

After completing file operations, the file should be closed using fclose($file); to free system resources. Always use error handling while opening files to avoid issues if the file doesn’t exist.

 

2.   Describe fread(), fgets(), and fgetc() functions in file handling?

PHP offers multiple functions for reading files:

•        fread() reads a specific number of bytes from a file. It is used to read the complete file or a large block of text.

Example:

$content = fread($file, filesize("demo.txt"));

•        fgets() reads a single line from the file until a newline character is encountered. It is used for line-by-line reading in loops. Example:

$line = fgets($file);

•        fgetc() reads a single character from the file at a time. It is used when precise control is needed. Example:

$char = fgetc($file);

These functions are useful based on how much content you need to read. Combine them with feof() to avoid reading beyond file end. Always close the file using fclose() after reading.

 

3.   How will you append text file in file operations?

Appending data means adding new content to the end of an existing file without overwriting it. To append in PHP, the file must be opened in 'a' (append) or 'a+' (append with read) mode using fopen().

Example:

$file = fopen("log.txt", "a"); fwrite($file, "New log entry.\n"); fclose($file);

•        fopen() opens the file in append mode.

•        fwrite() adds the new content at the end of the file.

•        fclose() closes the file to save changes and free memory.

Appending is useful for maintaining logs, adding records, or continuous updates without modifying the previous data. You can use condition checks to ensure the file exists before opening, and file_exists() function can help avoid errors. Always close the file after appending to ensure data integrity.

 

4.   How will you establish a connection to MySQL database?

In PHP, the mysqli_connect() function is used to connect to a MySQL database. You need to provide server name, username, password, and database name.

Example:

$conn = mysqli_connect("localhost", "root", "",

"school"); if (!$conn) {

  die("Connection failed: " . mysqli_connect_error());

}

Explanation:

•        "localhost" is the server where MySQL runs.

•        "root" is the MySQL username.

•        "" is the password (empty in localhost by default).

•        "school" is the database name.

After connection, you can perform queries using mysqli_query() and close the connection using mysqli_close($conn);. Always check if the connection was successful using conditionals. Use proper error handling to prevent the script from crashing.

 

5. How will you insert, delete and append a record in table?

To manage records in a MySQL table using PHP, we use SQL queries with mysqli_query().

Insert Record:

$sql = "INSERT INTO students (name, age) VALUES

('John', 20)";

mysqli_query($conn, $sql); Delete Record:

$sql = "DELETE FROM students WHERE id = 1"; mysqli_query($conn, $sql); Append (Update) Record:

$sql = "UPDATE students SET age = 22 WHERE id = 1"; mysqli_query($conn, $sql);

Inserting adds a new row. Deleting removes an existing row based on a condition. Updating modifies a row’s data. Always connect to the database before executing queries and use mysqli_close($conn); at the end. Add error handling using mysqli_error() for debugging. Use prepared statements for secure inputs.