How to Use fgets in PHP: Read Lines from a File Easily

In PHP, fgets reads a single line from an open file pointer until it reaches a newline or the specified length. You first open a file with fopen, then use fgets inside a loop to read each line until the end of the file.

Syntax

The fgets function reads a line from a file pointer. It takes two parameters:

• resource $handle: The file pointer returned by fopen.
• int $length (optional): Maximum number of bytes to read. If omitted, it reads up to the end of the line or up to 1024 bytes by default.

The function returns the line as a string or false on end of file or error.

php

string|false fgets(resource $handle, int $length = 1024);

Example

This example opens a text file named example.txt and reads it line by line using fgets. It prints each line until the file ends.

php

<?php
$filename = 'example.txt';
$handle = fopen($filename, 'r');
if ($handle) {
    while (($line = fgets($handle)) !== false) {
        echo $line;
    }
    fclose($handle);
} else {
    echo "Failed to open file.";
}
?>

Output

Hello, this is line one.
This is line two.
And this is line three.

Common Pitfalls

• Not checking if fopen succeeded before using fgets causes errors.
• Using fgets without a loop reads only one line.
• For binary files or very long lines, specifying $length is important to avoid memory issues.
• Remember to close the file with fclose to free resources.

php

<?php
// Wrong: Not checking fopen
$handle = fopen('file.txt', 'r');
$line = fgets($handle); // May cause error if fopen failed

// Right: Check fopen
$handle = fopen('file.txt', 'r');
if ($handle) {
    $line = fgets($handle);
    fclose($handle);
}
?>

Quick Reference

Function	Description
fopen($filename, 'r')	Open file for reading
fgets($handle, $length)	Read one line from file
feof($handle)	Check if end of file reached
fclose($handle)	Close the open file

Key Takeaways

Always open a file with fopen before using fgets to read lines.

Use fgets inside a loop to read the entire file line by line.

Check if fopen succeeded to avoid errors when reading.

Close the file with fclose after finishing reading.

Specify length in fgets to control memory for very long lines.