Mastering PHP’s ftell(): How to Track File Pointer Position Efficiently

In PHP programming, file read/write operations often require knowing the current file pointer position. The built‑in ftell() function returns the byte offset of the file pointer.

Function Overview

ftell(resource $handle): int

The function returns the current position of the file specified by $handle in the byte stream, or false on error.

Parameters

$handle

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

Return Value

Returns the current file pointer position as a byte offset, or false if an error occurs.

Example

<?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!";
}
?>

Running the above code with example.txt containing "Hello, World!" produces:

File content: Hello, Wor
File pointer position: 10

The script opens the file in read mode, reads the first ten bytes with fread(), prints the content, then uses ftell() to obtain and display the pointer position before closing the file.

Note that ftell() returns a byte offset; when a file is opened in text mode, characters such as Chinese characters may occupy multiple bytes, so the offset reflects bytes, not 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 combine it with other file functions for flexible processing, thereby improving code efficiency.