PHP gztell() Function: Usage and Examples

Use gztell() when you need to reports the current uncompressed-byte position in a gzip stream in a PHP application. The examples below show the actual operation and its limitations.

What Is gztell() in PHP?

Reports the current uncompressed-byte position in a gzip stream. The exact signature supported by your installation depends on its PHP version and enabled extensions.

Its syntax is:

gztell($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

$path = tempnam(sys_get_temp_dir(),"gzip_"); $file = gzopen($path,"wb"); gzwrite($file,"ABCDE"); gzclose($file); $file = gzopen($path,"rb"); gzread($file,2); echo gztell($file); gzclose($file); unlink($path);

Output:

2

Example 2: Different Input or Behavior

<?php

$path = tempnam(sys_get_temp_dir(),"gzip_"); $file = gzopen($path,"wb"); gzwrite($file,"01234"); gzclose($file); $file = gzopen($path,"rb"); gzseek($file,3); echo gztell($file); gzclose($file); unlink($path);

Output:

3

Practical Example: Applying the Function

<?php

$path = tempnam(sys_get_temp_dir(),"gzip_"); $file = gzopen($path,"wb"); gzwrite($file,"HEADERBODY"); gzclose($file); $file = gzopen($path,"rb"); gzread($file,6); echo "Payload offset: " . gztell($file); gzclose($file); unlink($path);

Output:

Payload offset: 6

Important Behavior and Edge Cases

The returned offset is in uncompressed bytes, not in the underlying compressed-file layout.

Comparison With Related Functions

Common Beginner Mistakes

Key Takeaways

• Reports the current uncompressed-byte position in a gzip stream.
• The returned offset is in uncompressed bytes, not in the underlying compressed-file layout.
• gzseek() sets a position; gztell() reads the current position.

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