Writing files (fwrite, file_put_contents) in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP code writing to a file?

Consider this PHP code that writes text to a file. What will be the content of the file example.txt after running this code?

PHP

<?php
$file = fopen('example.txt', 'w');
fwrite($file, "Hello");
fwrite($file, " World");
fclose($file);
?>

A The file contains: Hello\nWorld

B The file contains: HelloWorld

C The file contains: Hello World

D The file is empty

💡 Hint

Remember fwrite writes exactly what you give it without adding spaces.

The fwrite function writes the exact string given. Since "Hello" and " World" are written separately, the file content is concatenated as "Hello World" without any extra characters. Note the space before 'World' is part of the string.

❓ Predict Output

intermediate

What does file_put_contents write to the file?

What will be the content of data.txt after running this PHP code?

PHP

<?php
file_put_contents('data.txt', "Line1\nLine2");
?>

A

Line1
Line2

B Line1 Line2

C Line1\nLine2

D An empty file

💡 Hint

Check how PHP interprets escape sequences inside double quotes.

Inside double quotes, \n is interpreted as a newline character. So the file will contain two lines: 'Line1' and 'Line2' on separate lines.

🔧 Debug

advanced

Why does this fwrite code cause an error?

This PHP code tries to write to a file but causes an error. What is the cause?

PHP

<?php
$file = fopen('output.txt', 'r');
fwrite($file, "Test");
fclose($file);
?>

A fclose must be called before fwrite

B The file 'output.txt' does not exist, causing fwrite to fail

C fwrite requires the file to be opened in binary mode

D fopen mode 'r' opens file for reading only, so fwrite fails

💡 Hint

Check the fopen mode and what it allows.

Opening a file with mode 'r' means read-only. Writing with fwrite is not allowed and causes an error.

🧠 Conceptual

advanced

How does file_put_contents behave with FILE_APPEND flag?

What will be the content of log.txt after running this PHP code twice in a row?

PHP

<?php
file_put_contents('log.txt', "Entry1\n");
file_put_contents('log.txt', "Entry2\n", FILE_APPEND);
?>

A

Entry1
Entry2

B

Entry1
Entry1
Entry2

C

Entry1

D

Entry2

💡 Hint

FILE_APPEND adds content to the end of the file instead of overwriting.

The first call writes 'Entry1\n' overwriting any existing content. The second call appends 'Entry2\n' to the file. So the file contains both entries in order.

❓ Predict Output

expert

What is the number of bytes written by fwrite here?

Given this PHP code, what is the value of $bytes after fwrite runs?

PHP

<?php
$file = fopen('test.txt', 'w');
$bytes = fwrite($file, "Hello\nWorld");
fclose($file);
echo $bytes;
?>

A 12

B 11

C 10

D 5

💡 Hint

Count all characters including the newline.

The string "Hello\nWorld" has 11 characters: 5 letters in 'Hello', 1 newline, and 5 letters in 'World'. fwrite returns the number of bytes written, which is 11.