Reading files (fread, fgets, file) in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to open a file for reading.

PHP

<?php
$handle = fopen('example.txt', '[1]');
?>

Drag options to blanks, or click blank then click option'

Ax

Ba

Cr

Dw

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'w' which opens the file for writing and truncates it.

Using 'a' which opens the file for appending.

The mode 'r' opens the file for reading only.

2fill in blank

medium

Complete the code to read 100 bytes from the file.

PHP

<?php
$handle = fopen('example.txt', 'r');
$content = fread($handle, [1]);
fclose($handle);
?>

Drag options to blanks, or click blank then click option'

A0

B100

C200

D50

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 which reads nothing.

Using a smaller number like 50 which reads less than needed.

fread reads the specified number of bytes; here, 100 bytes.

3fill in blank

hard

Fix the error in the code to read one line from the file.

PHP

<?php
$handle = fopen('example.txt', 'r');
$line = [1]($handle);
fclose($handle);
?>

Drag options to blanks, or click blank then click option'

Afgets

Bfread

Cfile_get_contents

Dreadfile

Attempts:

3 left

💡 Hint

Common Mistakes

Using fread which reads bytes, not lines.

Using file_get_contents which reads the whole file.

fgets reads one line from the file handle.

4fill in blank

hard

Fill both blanks to read the entire file into an array of lines and print the first line.

PHP

<?php
$lines = [1]('example.txt');
[2] $lines[0];
?>

Drag options to blanks, or click blank then click option'

Afile

Bprint_r

Cecho

Dfgets

Attempts:

3 left

💡 Hint

Common Mistakes

Using fgets instead of file to read all lines.

Using print_r which prints array structure, not just the line.

The file function reads the file into an array of lines. echo prints the first line.

5fill in blank

hard

Fill all three blanks to open a file, read its entire content, and close it.

PHP

<?php
$handle = [1]('example.txt', 'r');
$content = [2]($handle, filesize('example.txt'));
fclose([3]);
?>

Drag options to blanks, or click blank then click option'

Afopen

Bfread

C$handle

Dfile_get_contents

Attempts:

3 left

💡 Hint

Common Mistakes

Using file_get_contents instead of fread when a handle is used.

Not closing the file handle.

Use fopen to open the file, fread to read the content, and fclose to close the file handle.

Practice

1. Which PHP function reads a file line by line, returning one line at a time?

easy

A. fopen()

B. fread()

C. file()

D. fgets()

Solution

1. Step 1: Understand function behavior

   fgets() reads a file one line at a time, useful for line-by-line processing.

2. Step 2: Compare with other functions

   fread() reads bytes, file() reads whole file into array, fopen() opens file but does not read.

3. Final Answer:

   fgets() -> Option D

4. Quick Check:

   Line-by-line reading = fgets() [OK]

Hint: fgets() reads one line at a time from a file [OK]

Common Mistakes:

• Confusing fread() with fgets()
• Thinking file() reads line by line
• Using fopen() to read data directly

2. Which of the following is the correct syntax to read 100 bytes from a file pointer $fp using fread()?

easy

A. fread($fp);

B. fread(100, $fp);

C. fread($fp, 100);

D. fread(100);

Solution

1. Step 1: Recall fread() parameter order

   fread() takes the file pointer first, then the number of bytes to read.

2. Step 2: Validate syntax correctness

   Only fread($fp, 100); matches the correct order and required parameters.

3. Final Answer:

   fread($fp, 100); -> Option C

4. Quick Check:

   fread(fp, bytes) syntax = fread($fp, 100); [OK]

Hint: fread() needs file pointer first, then byte count [OK]

Common Mistakes:

• Swapping parameters order
• Omitting byte count
• Passing only one argument

3. What will be the output of the following PHP code if the file data.txt contains:

Line1
Line2
Line3

Code:

$lines = file('data.txt');
echo trim($lines[1]);

medium

A. Line2

B. Line1

C. Line3

D. Error

Solution

1. Step 1: Understand file() output

   file() reads the whole file into an array, each element is a line including newline.

2. Step 2: Access second line and trim

   $lines[1] is the second line "Line2\n"; trim() removes newline, so output is "Line2".

3. Final Answer:

   Line2 -> Option A

4. Quick Check:

   file()[1] trimmed = Line2 [OK]

Hint: file() returns array of lines, index 1 is second line [OK]

Common Mistakes:

• Confusing array index starting at 0
• Not trimming newline characters
• Expecting fread() output instead

4. Identify the error in this PHP code snippet that tries to read the first 10 bytes of a file:

$fp = fopen('file.txt', 'r');
$content = fread(10, $fp);
echo $content;

medium

A. fopen() mode should be 'rb' instead of 'r'

B. Parameters of fread() are reversed

C. fread() requires a third parameter

D. fopen() returns false, file not opened

Solution

1. Step 1: Check fread() parameter order

   fread() expects file pointer first, then number of bytes. Here they are reversed.

2. Step 2: Confirm other parts

   fopen('file.txt', 'r') is valid for reading text files; no third parameter needed; no info about fopen failure.

3. Final Answer:

   Parameters of fread() are reversed -> Option B

4. Quick Check:

   fread(fp, bytes) order matters [OK]

Hint: fread() needs file pointer first, then bytes [OK]

Common Mistakes:

• Swapping fread() arguments
• Assuming fopen() mode error without evidence
• Expecting extra fread() parameters

5. You want to read a text file and print only the lines that contain the word "error" (case-insensitive). Which approach is best in PHP?

hard

A. Use fgets() in a loop, check each line with stripos()

B. Use fread() to read entire file as bytes, then search for "error"

C. Use file() to read all lines, then loop and check each line with stripos()

D. Use fopen() and print file pointer directly

Solution

1. Step 1: Consider memory and line processing

   fgets() reads line by line, efficient for large files and allows checking each line.

2. Step 2: Use stripos() for case-insensitive search

   Inside the loop, stripos() finds "error" ignoring case, so only matching lines are printed.

3. Final Answer:

   Use fgets() in a loop, check each line with stripos() -> Option A

4. Quick Check:

   Line-by-line read + case-insensitive check = fgets() + stripos() [OK]

Hint: Use fgets() loop with stripos() for line filtering [OK]

Common Mistakes:

• Using fread() for line filtering
• Reading whole file into memory unnecessarily
• Printing file pointer instead of content