PHP ftell() Function: Usage and Examples

Use ftell() when you need to returns the current byte offset of a stream pointer in a PHP application. The examples below show the actual operation and its limitations.

What Is ftell() in PHP?

Returns the current byte offset of a stream pointer. The exact signature supported by your installation depends on its PHP version and enabled extensions.

Its syntax is:

ftell($stream): int|false

Parameters and return value: The parameter types, optional arguments, references, and return type are shown in the signature above. Optional parameters are marked with an ellipsis in this reference signature.

Example 1: Basic Usage

<?php

$stream = fopen("php://temp","w+"); fwrite($stream,"Hello"); echo ftell($stream); fclose($stream);

Output:

5

Example 2: Different Input or Behavior

<?php

$stream = fopen("php://temp","w+"); fwrite($stream,"ABCDE"); rewind($stream); fread($stream,2); echo ftell($stream); fclose($stream);

Output:

2

Practical Example: Applying the Function

<?php

$stream = fopen("php://temp","w+"); fwrite($stream,"HEADER:BODY"); rewind($stream); $header = fread($stream,7); echo "Body begins at byte " . ftell($stream); fclose($stream);

Output:

Body begins at byte 7

Important Behavior and Edge Cases

Offsets are bytes, not Unicode characters; stream wrappers may be non-seekable.

Comparison With Related Functions

Common Beginner Mistakes

Key Takeaways

• Returns the current byte offset of a stream pointer.
• Offsets are bytes, not Unicode characters; stream wrappers may be non-seekable.
• fseek() moves the stream pointer; ftell() reads its current position.

Use ftell() for the specific operation demonstrated above. Check its prerequisites and handle failure conditions before using it with production data.