File pointer manipulation in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP code using file pointer?

Consider the following PHP code that reads a file pointer position after some operations. What will it output?

PHP

<?php
$file = fopen('php://memory', 'r+');
fwrite($file, "Hello World");
fseek($file, 6);
echo ftell($file);
fclose($file);
?>

A 6

B 11

C 0

D 5

💡 Hint

ftell() returns the current position of the file pointer after fseek().

The code writes 'Hello World' (11 characters) to the file, then moves the pointer to position 6 with fseek(). ftell() then returns 6, the current pointer position.

❓ Predict Output

intermediate

What does this PHP code output after reading with file pointer?

Given this PHP code, what will be printed?

PHP

<?php
$file = fopen('php://memory', 'r+');
fwrite($file, "abcdef");
fseek($file, 2);
echo fread($file, 3);
fclose($file);
?>

A cde

B abc

C bcd

D def

💡 Hint

fseek moves pointer to position 2, fread reads 3 bytes from there.

The string 'abcdef' is written. Pointer moves to position 2 (0-based), which is 'c'. Reading 3 bytes from there gives 'cde'.

❓ Predict Output

advanced

What is the output of this PHP code using rewind and ftell?

Analyze this PHP code snippet. What will it output?

PHP

<?php
$file = fopen('php://memory', 'r+');
fwrite($file, "12345");
fseek($file, 4);
rewind($file);
echo ftell($file);
fclose($file);
?>

A 5

B 4

C 0

D 1

💡 Hint

rewind() moves the pointer back to the start of the file.

After writing '12345', pointer moves to position 4. rewind() resets pointer to 0. ftell() then returns 0.

❓ Predict Output

advanced

What error or output does this PHP code produce?

What happens when this PHP code runs?

PHP

<?php
$file = fopen('php://memory', 'r');
fseek($file, 5);
fwrite($file, "test");
fclose($file);
?>

A Warning: fwrite() expects parameter 1 to be resource, bool given

B Warning: fwrite(): supplied resource is not writable

C No output, file pointer moved and wrote successfully

D Fatal error: fseek() expects parameter 1 to be resource

💡 Hint

The file is opened in read-only mode but fwrite is called.

Opening with 'r' mode means read-only. fwrite() on a read-only stream triggers a warning about the resource not being writable.

🧠 Conceptual

expert

How many bytes are read and what is the pointer position after this PHP code?

Consider this PHP code snippet. How many bytes does fread() read, and what is the file pointer position after reading?

PHP

<?php
$file = fopen('php://memory', 'r+');
fwrite($file, "OpenAI GPT");
fseek($file, 4);
$data = fread($file, 10);
$pos = ftell($file);
fclose($file);
echo strlen($data) . ',' . $pos;
?>

A 7,11

B 7,10

C 10,14

D 6,10

💡 Hint

fread reads up to the end of file or requested bytes, pointer moves accordingly.

The string 'OpenAI GPT' is 10 bytes. Pointer moves to 4 ('A'). Reading 10 bytes but only 6 bytes remain to EOF ('AI GPT'), so fread reads 6 bytes. Pointer moves to position 10.