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

In PHP programming, file read/write operations often require knowing the current file pointer position, which can be obtained using the ftell() function.

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.

Parameters:

$handle

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

Return Value:

Returns the byte offset of the current file pointer, or false on failure.

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!";
}
?>

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

File content: Hello, Wor
File pointer position: 10

The script opens the file with fopen(), reads 10 bytes using fread(), prints the content, then calls ftell() to get the pointer position, prints it, 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 reflects bytes, not characters.

Conclusion

The ftell() function is a practical 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.