Writing files (fwrite, file_put_contents) in PHP - Mini Project: Build & Apply

Writing files with fwrite and file_put_contents in PHP

📖 Scenario: You are creating a simple PHP script to save user notes into a text file on the server. This is like writing a diary entry or saving a shopping list.

🎯 Goal: Build a PHP script that writes a string into a file using two methods: fwrite and file_put_contents.

📋 What You'll Learn

Create a variable with the filename 'notes.txt'.

Create a variable with the text content to save.

Use fwrite to write the content into the file.

Use file_put_contents to write the content into the file.

Print a confirmation message after writing.

💡 Why This Matters

🌍 Real World

Writing files is common when saving user data, logs, or configuration settings on a server.

💼 Career

Many web developers need to handle file operations safely and efficiently to store and retrieve data.

1

Create filename and content variables

Create a variable called $filename and set it to the string 'notes.txt'. Then create a variable called $content and set it to the string 'Today I learned how to write files in PHP.'.

PHP

<?php

// Create $filename and $content variables
// Your code here

Hint

Use = to assign the string values to the variables.

2

Open file and write content using fwrite

Add code to open the file $filename for writing using fopen with mode 'w'. Then use fwrite to write the $content into the file. Finally, close the file with fclose.

PHP

<?php
$filename = 'notes.txt';
$content = 'Today I learned how to write files in PHP.';

// Open file and write content using fwrite
// Your code here

Hint

Use fopen to open the file, then fwrite to write, and fclose to close it.

3

Write content using file_put_contents

Add code to write the $content into the file $filename using the function file_put_contents. This function writes the entire string to the file in one step.

PHP

<?php
$filename = 'notes.txt';
$content = 'Today I learned how to write files in PHP.';
$file = fopen($filename, 'w');
fwrite($file, $content);
fclose($file);

// Write content using file_put_contents
// Your code here

Hint

Use file_put_contents with the filename and content as arguments.

4

Print confirmation message

Add a print statement to display the message 'File written successfully.' after writing the content.

PHP

<?php
$filename = 'notes.txt';
$content = 'Today I learned how to write files in PHP.';
$file = fopen($filename, 'w');
fwrite($file, $content);
fclose($file);
file_put_contents($filename, $content);

// Print confirmation message
// Your code here

Hint

Use print('File written successfully.'); to show the message.

Practice

1. Which PHP function is best for quickly writing a string to a file without manually opening or closing it?

easy

A. fclose

B. fwrite

C. fopen

D. file_put_contents

Solution

1. Step 1: Understand the purpose of file_put_contents

   This function writes data to a file in one step, handling opening and closing automatically.

2. Step 2: Compare with fwrite

   fwrite requires manual file opening and closing, so it's not as quick for simple writes.

3. Final Answer:

   file_put_contents -> Option D

4. Quick Check:

   Quick file write = file_put_contents [OK]

Hint: Use file_put_contents for quick file writes without fopen/fclose [OK]

Common Mistakes:

• Confusing fwrite as a standalone write function
• Thinking fopen writes data
• Assuming fclose writes data

2. Which of the following is the correct syntax to write "Hello" to a file named "greet.txt" using fwrite?

easy

A. $file = fopen('greet.txt'); fwrite($file, 'Hello');

B. $file = fopen('greet.txt', 'w'); fwrite($file, 'Hello'); fclose($file);

C. file_put_contents('greet.txt', 'Hello');

D. fwrite('greet.txt', 'Hello');

Solution

1. Step 1: Check the correct usage of fwrite

   fwrite requires a file handle from fopen opened in write mode.

2. Step 2: Validate the full sequence

   $file = fopen('greet.txt', 'w'); fwrite($file, 'Hello'); fclose($file); opens the file in write mode, writes "Hello", then closes the file properly.

3. Final Answer:

   $file = fopen('greet.txt', 'w'); fwrite($file, 'Hello'); fclose($file); -> Option B

4. Quick Check:

   fopen + fwrite + fclose = correct syntax [OK]

Hint: Always fopen with 'w' before fwrite, then fclose [OK]

Common Mistakes:

• Calling fwrite without fopen file handle
• Missing file mode in fopen
• Not closing the file after writing

3. What will be the output of this PHP code?

$filename = 'data.txt';
file_put_contents($filename, "Line1\n");
$file = fopen($filename, 'a');
fwrite($file, "Line2\n");
fclose($file);
echo file_get_contents($filename);

medium

A. Line2

B. Line1

C. Line1
Line2

D. Error: file not found

Solution

1. Step 1: Analyze file_put_contents call

   This writes "Line1\n" to 'data.txt', creating or overwriting the file.

2. Step 2: Analyze fopen with 'a' mode and fwrite

   Opening in append mode adds "Line2\n" after existing content.

3. Step 3: Read file content with file_get_contents

   It returns both lines concatenated with newlines.

4. Final Answer:

   Line1 Line2 -> Option C

5. Quick Check:

   Append mode adds lines, so both lines appear [OK]

Hint: file_put_contents overwrites; fopen 'a' appends [OK]

Common Mistakes:

• Assuming file_put_contents appends instead of overwrites
• Forgetting 'a' mode appends
• Expecting only last line output

4. Identify the error in this PHP code snippet that tries to write "Test" to "file.txt":

$file = fopen('file.txt', 'r');
fwrite($file, 'Test');
fclose($file);

medium

A. File opened in read mode, cannot write

B. Missing semicolon after fwrite

C. fclose called before fwrite

D. fopen filename missing extension

Solution

1. Step 1: Check fopen mode

   The file is opened in 'r' (read) mode, which does not allow writing.

2. Step 2: Understand fwrite requirements

   Writing requires 'w', 'a', or 'r+' mode; 'r' mode causes error on fwrite.

3. Final Answer:

   File opened in read mode, cannot write -> Option A

4. Quick Check:

   Write needs write mode, not 'r' [OK]

Hint: Open file with 'w' or 'a' to write, not 'r' [OK]

Common Mistakes:

• Using 'r' mode when writing
• Ignoring file mode errors
• Assuming fwrite works on read-only handle

5. You want to save user input lines into a file, but only if the input is not empty or whitespace. Which PHP code snippet correctly writes non-empty trimmed lines to "input.txt" using fwrite?

hard

A. $file = fopen('input.txt', 'w'); foreach ($lines as $line) { if (trim($line) !== '') { fwrite($file, $line . "\n"); } } fclose($file);

B. $file = fopen('input.txt', 'w'); foreach ($lines as $line) { fwrite($file, $line . "\n"); } fclose($file);

C. file_put_contents('input.txt', implode("\n", $lines));

D. $file = fopen('input.txt', 'r'); foreach ($lines as $line) { if ($line) { fwrite($file, $line); } } fclose($file);

Solution

1. Step 1: Check file open mode

   $file = fopen('input.txt', 'w'); foreach ($lines as $line) { if (trim($line) !== '') { fwrite($file, $line . "\n"); } } fclose($file); opens file in 'w' mode, allowing writing and overwriting.

2. Step 2: Validate input filtering

   It uses trim($line) !== '' to skip empty or whitespace-only lines before writing.

3. Step 3: Confirm writing and closing

   Writes each valid line with newline and closes file properly.

4. Final Answer:

   Option A code snippet -> Option A

5. Quick Check:

   Trim check + fwrite + 'w' mode = correct [OK]

Hint: Trim input lines and write only non-empty with fwrite [OK]

Common Mistakes:

• Not trimming lines before writing
• Opening file in 'r' mode when writing
• Using file_put_contents without filtering