Master PHP’s ftell(): How to Get File Pointer Position with Code Examples

In PHP programming, reading and writing files often requires knowing the current file pointer position; the ftell() function provides this capability.

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

Function Overview:

ftell(resource $handle): int

The function returns the current position of the file pointer in the byte stream for the handle provided, or 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 on failure.

Code Example:

The following example reads the first 10 bytes of a file and obtains the pointer position using ftell():

<?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

The script opens the file with fopen(), reads 10 bytes with fread(), prints the content, then uses ftell() to retrieve and display the pointer position, and finally closes the file with fclose().

Note that ftell() returns the byte offset; when a file is opened in text mode, characters such as Chinese characters may occupy multiple bytes, so the offset is calculated in bytes.

Conclusion:

The ftell() function is a useful tool in PHP file operations, allowing developers to obtain the current file pointer position and combine it with other file functions to enhance code efficiency.