PHP SplFileObject fseek() Function

The SplFileObject::fseek() function is an inbuilt function of Standard PHP Library (SPL) in PHP that allows you to move the file pointer to a specified position within a file opened using SplFileObject. The file pointer is the position where the next read or write operation will occur. This function is used to navigate within a file and read or write data from a specific location.

Syntax:

public SplFileObject::fseek(int $offset, int $whence = SEEK_SET): int

Parameters: This function accepts two parameters that are described below.

• $offset: The offset value represents the number of bytes to move the file pointer. It can be positive or negative, depending on the direction you want to move the pointer.
• $whence: This is an optional parameter that specifies the starting point for the offset calculation. It can take one of the following values: SEEK_SET - Set position equal to offset bytes, SEEK_CUR - Set position to current location plus offset, SEEK_END - Set position to end-of-file plus offset.

Program 1: The following program demonstrates the SplFileObject::fseek() function. Save this file name as "output.txt" before running this program.

Line 1: This is the first line of data.
Line 2: This is the second line of data.
Line 3: This is the third line of data.

<?php

 $file = new SplFileObject('./output.txt', 'r');
 
// Move the file pointer to the 10th byte 
// from the beginning of the file.
$file->fseek(10, SEEK_SET);

// Read the content from the current position
//(10th byte) to the end of the file.
$content = $file->fread($file->getSize() - $file->ftell()); 
echo $content;

?>  

Output:

is is the first line of data.
Line 2: This is the second line of data.
Line 3: This is the third line of data.

Program 2: The following program demonstrates the SplFileObject::fseek() function. Save this file name as "output.txt" before running this program.

Ram 
Seeta
Michael Johnson
Emily Brown
William Davis

<?php
    
$file = new SplFileObject('output.txt', 'r');

// Move the file pointer to the beginning
// of the third line (name)
$file->fseek(strlen("Michael \n") * 2, SEEK_SET);
   
// Read the third name from the current position.
$thirdName = trim($file->fgets());
   
// Output the third name.
echo "The third name in the file is: " . $thirdName;   
  
?>

Output:

The third name in the file is: Johnson                                                                                            

Reference: https://www.php.net/manual/en/splfileobject.fseek.php