Using PHP ftell() to Retrieve the Current File Pointer Position

In PHP programming, file read/write operations often require knowing the current position of the file pointer, and the ftell() function conveniently provides this information.

This article introduces the usage of ftell() with code examples.

Function Overview

ftell(resource $handle): int

The function returns the current byte offset of the file associated with the $handle resource. It returns false on error.

Parameter Description

$handle

: File resource handle obtained via fopen() or similar functions.

Return Value

Returns the byte offset of the current file pointer, or false if an error occurs.

Code Example

The following example uses ftell() to read the first 10 bytes of a file and obtain the pointer position:

<?php
$filename = "example.txt";
$handle = fopen($filename, "r");

if ($handle) {
    $content = fread($handle, 10);
    echo "File content: " . $content . "<br/>";

    $position = ftell($handle);
    echo "File pointer position: $position";

    fclose($handle);
} else {
    echo "Unable to open file!";
}
?>

Assuming example.txt contains "Hello, World!", the output is:

File content: Hello, Wor
File pointer position: 10

In the code, fopen() opens the file in read‑only mode, fread() reads the first ten bytes into $content, and ftell() retrieves the current pointer offset, storing it in $position. Finally, fclose() closes the file.

Note that ftell() returns the byte offset; when a file is opened in text mode, multibyte characters (e.g., Chinese characters) occupy multiple bytes, so the offset reflects bytes rather than characters.

Conclusion

The ftell() function is a very useful tool in PHP file operations, allowing developers to easily obtain the current file pointer position and perform subsequent processing based on that location, thereby improving code efficiency.