Reading files (fread, fgets, file) in PHP - Mini Project: Build & Apply

Reading files (fread, fgets, file)

📖 Scenario: You have a text file named quotes.txt that contains several inspirational quotes, one per line. You want to read this file in different ways using PHP to understand how file reading works.

🎯 Goal: Learn how to read a file using fread, fgets, and file functions in PHP by creating a script that reads and displays the contents of quotes.txt step-by-step.

📋 What You'll Learn

Create a file handle to open quotes.txt for reading

Use fread to read the entire file content

Use fgets to read the file line by line

Use file function to read all lines into an array

Print the results after each reading method

💡 Why This Matters

🌍 Real World

Reading files is a common task in web development, such as loading configuration files, logs, or user data stored in text files.

💼 Career

Understanding file reading methods in PHP is essential for backend developers working with file systems, data processing, and server-side scripting.

1

Open the file quotes.txt for reading

Create a variable called file and open quotes.txt in read mode using fopen.

PHP

<?php
// Your code here

Hint

Use fopen with the filename "quotes.txt" and mode "r" to open the file for reading.

2

Read the entire file content using fread

Create a variable called content and use fread with $file and filesize("quotes.txt") to read the whole file content.

PHP

<?php
$file = fopen("quotes.txt", "r");
// Your code here

Hint

Use fread with the file handle $file and the size of the file using filesize("quotes.txt").

3

Read the file line by line using fgets

Create a variable called lines as an empty array. Use a while loop with fgets($file) to read each line and append it to lines. Close the file after reading.

PHP

<?php
$file = fopen("quotes.txt", "r");
$content = fread($file, filesize("quotes.txt"));
// Your code here

Hint

Use rewind($file) to reset the file pointer before reading lines. Then use a while loop with fgets to read each line until the end of the file. Don't forget to close the file with fclose.

4

Read all lines at once using file and print all results

Create a variable called allLines and assign it the result of file("quotes.txt"). Then print content, lines, and allLines using print_r inside <pre> tags for readability.

PHP

<?php
$file = fopen("quotes.txt", "r");
$content = fread($file, filesize("quotes.txt"));

rewind($file);
$lines = [];
while (($line = fgets($file)) !== false) {
    $lines[] = $line;
}
fclose($file);

// Your code here

Hint

Use file("quotes.txt") to read all lines into an array. Use print_r inside <pre> tags to print content, lines, and allLines clearly.

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