PHP Filesystem fseek() Function

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The PHP Filesystem fseek() function is used to seek in an open file. This function can move file pointer from its current position to a new position forward or backward, given by the number of bytes. This function can return 0 on success or -1 on failure. Seeking past EOF can not produce an error.

Syntax

Below is the syntax of the PHP Filesystem fseek() function −

int fseek ( resource $handle , int $offset [, int $whence = SEEK_SET ] )

Parameters

Here are the required and optional parameters of the fseek() function −

Return Value

If successful, fseek() returns 0 and if there is an error, it returns -1.

PHP Version

The fseek() function was first introduced as part of core PHP 4 and work well with the PHP 5, PHP 7, PHP 8.

Example

The PHP Filesystem fseek() Function is used to show the basic usage in this example. View the following PHP code −

<?php
   $file = fopen("/Path/To/The/File", "mode");
   echo fseek($file, 10, SEEK_CUR);
?>

Example

This code shows how to read a text file from start to finish, starting at the beginning and ending at the end by using fseek() function. The code also uses fopen() and fgets() functions.

<?php
   $file = fopen("/PhpProject/sample.txt", "r");
   
   // read first line
   echo fgets($file);
   
   // move back to beginning of file
   fseek($file, 0);
   
   echo fgets($file);
   
?>

Output

Here is the output of the above code −

Tutorialspoint
Tutorialspoint

Example

This example shows how to use fseek() to shift the pointer to the end of the file in order to read the last line of a file.

<?php
   //Open the file
   $file = fopen("data.txt", "r");
   
   //Move the file pointer
   fseek($file, 0, SEEK_END);

   //Read the last line
   $lastLine = fgets($file);

   //Print the last line
   echo $lastLine;

   //Close the file
   fclose($file);
?> 

Output

This will produce the following result −

Tutorialspoint

Example

This sample shows how to read a file using fseek() function that has had the first 50 characters skipped. So for this we have used SEEK_SET parameter.

<?php
   $file = fopen("myfile.txt", "r");

   //Skip 50 characters
   fseek($file, 50, SEEK_SET);

   //Store content after skipping 50 characters
   $contentAfterSkipping = fgets($file);

   //Print the result
   echo $contentAfterSkipping;

   //Close the file
   fclose($file);
?> 

Output

This will produce the following result after skipping 50 characters −

ork is very important.

Example

This example demonstrates how to write data to designated places inside a file with the help of fseek() function.

<?php
   $file = fopen("myfile.txt", "r+");
   fwrite($file, "Important note:");
   fseek($file, 15, SEEK_SET);
   fwrite($file, " Don't forget to submit report");
   fclose($file);
?> 

Output

This will produce the following result −

Hello World!!!!!

Today is 6 June 2024 and I am working on PHP functions.

Don't forget to submit report

Note

The starting position can be designated as SEEK_SET (the starting point of the file), SEEK_END (the end of the file), or SEEK_CUR (the pointer's current address). SEEK_SET is assumed by default if it is not provided.

Summary

Use PHP's fseek() function to move the file pointer to a given spot inside a file. Understanding how to use PHP successfully is necessary in order to access and edit file contents in applications.