PHP gzrewind() Function: Usage and Examples

Use gzrewind() when you need to moves a gzip stream pointer back to the beginning in a PHP application. The examples below show the actual operation and its limitations.

What Is gzrewind() in PHP?

Moves a gzip stream pointer back to the beginning. The exact signature supported by your installation depends on its PHP version and enabled extensions.

Its syntax is:

gzrewind($stream): bool

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($file,"ABC"); gzclose($file); $file = gzopen($path,"rb"); gzread($file,2); gzrewind($file); echo gzread($file,3); gzclose($file); unlink($path);

Output:

ABC

Example 2: Different Input or Behavior

<?php

$path = tempnam(sys_get_temp_dir(),"gzip_"); $file = gzopen($path,"wb"); gzwrite($file,"repeat"); gzclose($file); $file = gzopen($path,"rb"); gzread($file,6); gzrewind($file); echo gzread($file,6); gzclose($file); unlink($path);

Output:

repeat

Practical Example: Applying the Function

<?php

$path = tempnam(sys_get_temp_dir(),"gzip_"); $file = gzopen($path,"wb"); gzwrite($file,"log"); gzclose($file); $file = gzopen($path,"rb"); echo gzread($file,3); gzrewind($file); echo ":" . gzread($file,3); gzclose($file); unlink($path);

Output:

log:log

Important Behavior and Edge Cases

Rewinding affects the gzip stream pointer; it does not change the compressed file.

Comparison With Related Functions

Common Beginner Mistakes

Key Takeaways

• Moves a gzip stream pointer back to the beginning.
• Rewinding affects the gzip stream pointer; it does not change the compressed file.
• gzseek() positions a gzip stream at a chosen uncompressed-byte offset.

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