gzfile and readgzfile no longer identify corrupted gzip data

Description

Using this (invalid) gzip file: corrupt.txt.gz for testing below.

Just for completion: this is what happens using zcat/gzip - it can't decode it and thinks it's encrypted. It's not, it's just garbage.

$ zcat corrupt.txt.gz
gzip: corrupt.txt.gz is encrypted -- not supported

The following code:

<?php
var_dump(gzfile("corrupt.txt.gz"));

Resulted in this output:

array(2) {
  [0]=>
  string(8) "x��	U"
  [1]=>
  string(6) "I-.��"
}

But I expected this output instead:

array(0) {
}

Running the same code with PHP < 8.5.3 (including 8.5.2) will result in the expected empty array.

The same issue exists when using readgzfile(): all older versions will return -1 while 8.5.3 returns binary data.

PHP Version

PHP 8.5.3 (cli) (built: Feb 12 2026 16:29:14) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.5.3, Copyright (c) Zend Technologies
    with Xdebug v3.5.1, Copyright (c) 2002-2026, by Derick Rethans
    with Zend OPcache v8.5.3, Copyright (c), by Zend Technologies

Operating System

ArchLinux

Start by reproducing the supplied corrupt.txt.gz case with gzfile() and readgzfile() on PHP 8.5.2 and 8.5.3. Trace the gzip handling used by these functions and compare the corrupted-data result with the expected empty array and -1 return values; done means both functions reject the invalid stream as before.