Description
Description
After upgrading to PHP 8.5.9, I am seeing apparent OPcache corruption under PHP-FPM where PHP executes a different internal function than the one present in the source code.
Examples from production:
Source code contains a call equivalent to:
number_format($latitude, 2)
but PHP throws:
ArgumentCountError: dechex() expects exactly 1 argument, 2 given
Stack trace:
#0 /home/.../src/Weather/templates/event-tracking.php(26): dechex('23.00000000', 2)
#1 /home/.../src/Weather/EventController.php(886): require_once(...)
#2 /home/.../public_html/weather/tropical-weather-events/2024-joyce.php(5): include(...)
#3 {main}
There is no dechex() call at this location in the source.
I have also received similar errors involving hypot(), where the source contains a different math function.
In addition to exceptions, some requests return mathematically incorrect numeric results without throwing an exception.
The problem occurs on both the production site and a test subdomain using the same application code.
OPcache/JIT testing
Initial configuration:
opcache.enable=1
opcache.validate_timestamps=1
opcache.revalidate_freq=15
opcache.jit=tracing
opcache.jit_buffer_size=128M
PHP:
PHP 8.5.9
ea-php85-php-8.5.9-2.3.1.cpanel
PHP-FPM / fpm-fcgi
Linux x86_64
cPanel EasyApache 4
JIT status showed tracing JIT enabled.
I first changed:
and restarted PHP-FPM.
The ArgumentCountError occurrences initially stopped, but incorrect numeric results later continued while OPcache remained enabled.
Redis/application caches were completely cleared and the incorrect numeric results remained.
Calling opcache_invalidate() on the affected PHP files immediately caused the same source code to begin producing correct results again.
Editing an affected source file and then restoring exactly the same PHP statement also caused the problem to temporarily disappear after OPcache recompiled the file.
Flushing OPcache caused behavior to change again. Some previously incorrect pages became correct, while wrong-function errors began occurring on other production requests.
Finally I set:
and restarted PHP-FPM.
With OPcache completely disabled, both production and test have so far produced correct calculations and no wrong-function ArgumentCountErrors despite repeatedly loading the affected pages.
OPcache entry observed while problem was occurring
For one affected template:
Disk file:
mtime raw: 1786984725
size: 15902
md5: 3c9038dd4c9b0ba4e809cc60ddb1e45b
OPcache entry:
hits: 21
memory_consumption: 17104
last_used_timestamp: 1787045955
timestamp: 1786984725
revalidate: 1787045970
The OPcache timestamp exactly matched the filesystem mtime.
Version timing
Current PHP package:
Version: 8.5.9
Release: 2.3.1.cpanel
Install Date: Thu 13 Aug 2026 12:37:25 AM CDT
The issue was first noticed after this update when an affected template was edited and therefore recompiled by OPcache.
Expected result
PHP should execute:
number_format('23.00000000', 2)
Actual result
PHP sometimes executes an unrelated internal function using the same arguments:
resulting in:
ArgumentCountError: dechex() expects exactly 1 argument, 2 given
Disabling OPcache appears to eliminate the problem.
Additional information
APCu is not installed or enabled.
Cloudflare was ruled out for the incorrect page output:
Redis was completely flushed without resolving the incorrect numeric results.
Restarting PHP-FPM and/or invalidating specific OPcache entries changes the behavior.
The same application behaves correctly with OPcache disabled.
PHP Version
PHP 8.5.9 (cli) (built: Aug 12 2026 20:52:36) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.5.9, Copyright (c) Zend Technologies
with Zend OPcache v8.5.9, Copyright (c), by Zend Technologies
Operating System
AlmaLinux 8.10 x86_64
Description
Description
After upgrading to PHP 8.5.9, I am seeing apparent OPcache corruption under PHP-FPM where PHP executes a different internal function than the one present in the source code.
Examples from production:
Source code contains a call equivalent to:
but PHP throws:
Stack trace:
There is no dechex() call at this location in the source.
I have also received similar errors involving hypot(), where the source contains a different math function.
In addition to exceptions, some requests return mathematically incorrect numeric results without throwing an exception.
The problem occurs on both the production site and a test subdomain using the same application code.
OPcache/JIT testing
Initial configuration:
PHP:
JIT status showed tracing JIT enabled.
I first changed:
and restarted PHP-FPM.
The ArgumentCountError occurrences initially stopped, but incorrect numeric results later continued while OPcache remained enabled.
Redis/application caches were completely cleared and the incorrect numeric results remained.
Calling opcache_invalidate() on the affected PHP files immediately caused the same source code to begin producing correct results again.
Editing an affected source file and then restoring exactly the same PHP statement also caused the problem to temporarily disappear after OPcache recompiled the file.
Flushing OPcache caused behavior to change again. Some previously incorrect pages became correct, while wrong-function errors began occurring on other production requests.
Finally I set:
and restarted PHP-FPM.
With OPcache completely disabled, both production and test have so far produced correct calculations and no wrong-function ArgumentCountErrors despite repeatedly loading the affected pages.
OPcache entry observed while problem was occurring
For one affected template:
Disk file:
OPcache entry:
The OPcache timestamp exactly matched the filesystem mtime.
Version timing
Current PHP package:
The issue was first noticed after this update when an affected template was edited and therefore recompiled by OPcache.
Expected result
PHP should execute:
Actual result
PHP sometimes executes an unrelated internal function using the same arguments:
resulting in:
Disabling OPcache appears to eliminate the problem.
Additional information
APCu is not installed or enabled.
Cloudflare was ruled out for the incorrect page output:
Redis was completely flushed without resolving the incorrect numeric results.
Restarting PHP-FPM and/or invalidating specific OPcache entries changes the behavior.
The same application behaves correctly with OPcache disabled.
PHP Version
Operating System
AlmaLinux 8.10 x86_64