Description:
------------
This only happens when PHP is built with `--enable-debug`, and it's only a notice. Possibly, it's deliberate.

`php -d memory_limit=5M test.php` on the attached script will run the script successfully, and while php is shutting down, php will internally reset original ini settings, including memory_limit. This will trigger an error because the restored memory_limit is smaller than the amount of memory recorded as being in use at the time - this is more likely to affect programs with data structures that can't be garbage collected
(gc_disable(); public function __construct() { $this->x = [$this]; })

```
(gdb) b zend_error
Breakpoint 1 at 0x613f69: file /path/to/php-src/Zend/zend.c, line 1561.
(gdb) run
Starting program: /path/to/php-8.1.0-debug-intersection-types-install/bin/php -d memory_limit=5M test.php
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Memory usage before shutting down: 11975904

Breakpoint 1, zend_error (type=21845, format=0x555556379140 "\001") at /path/to/php-src/Zend/zend.c:1561
1561    ZEND_API ZEND_COLD void zend_error(int type, const char *format, ...) {
(gdb) bt
#0  zend_error (type=21845, format=0x555556379140 "\001") at /path/to/php-src/Zend/zend.c:1561
#1  0x0000555555ac1824 in OnChangeMemoryLimit (entry=0x55555637ebe0, new_value=0x55555637ec60, mh_arg1=0x0, mh_arg2=0x0, mh_arg3=0x0, stage=8) at /path/to/php-src/main/main.c:276
#2  0x0000555555c1d8eb in zend_restore_ini_entry_cb (ini_entry=0x55555637ebe0, stage=8) at /path/to/php-src/Zend/zend_ini.c:54
#3  0x0000555555c1db8c in zend_ini_deactivate () at /path/to/php-src/Zend/zend_ini.c:129
#4  0x0000555555b672ac in zend_deactivate () at /path/to/php-src/Zend/zend.c:1290
#5  0x0000555555ac4d17 in php_request_shutdown (dummy=0x0) at /path/to/php-src/main/main.c:1823
#6  0x0000555555cd21d2 in do_cli (argc=4, argv=0x555556378cb0) at /path/to/php-src/sapi/cli/php_cli.c:1134
#7  0x0000555555cd2ab6 in main (argc=4, argv=0x555556378cb0) at /path/to/php-src/sapi/cli/php_cli.c:1366
```

Perhaps the memory_limit should be a special case, and only be restored after everything else shuts down, and memory is freed?


This is emitted as a notice to stdout when running https://github.com/phan/phan to self-analyze itself in php 8.1 with the default memory limit of 138 MB (phan generates cyclic data structures in some places, such as union type representations)

Test script:
---------------
<?php
// Run this with `php -d memory_limit=5M test.php`
class X {
    public $x;
    public function __construct() { $this->x = [$this]; }
}
gc_disable();
ini_set('memory_limit', '1G');
$y = [];
for ($i = 0; $i < 20000; $i++) {
    $y[] = new X();
}
$y[0]->y = &$y;
$y[0]->z = $x;
echo "Memory usage before shutting down: " . memory_get_usage() . "\n";

// Observed in php 8.1:
// Warning: Failed to set memory limit to 5242880 bytes (Current memory usage is 12582912 bytes) in Unknown on line 0


Expected result:
----------------
No warning should be emitted during shutdown for a request

Actual result:
--------------
`Warning: Failed to set memory limit to 5242880 bytes (Current memory usage is 12582912 bytes) in Unknown on line 0` is emitted when php automatically tries to restore the system memory limit (`php -d memory_limit=5M`)