preg_match and preg_match_all both do not set $matches on regex fail, leaving as it was set prior to call

Description

The following code:

<?php // preg_match_all.php
$matches = [0 => 'Orange',
            1 => 'Apple',
            2 => 'Banana',
            3 => 'Monkey'];
$result = preg_match_all('aeiou{0,', 'ou', $matches);
var_dump($result);
var_dump($matches);

$result = preg_match('aeiou{0,', 'ou', $matches);
var_dump($result);
var_dump($matches);

Resulted in this output from command line %php preg_match_all.php:

PHP Warning:  preg_match_all(): Delimiter must not be alphanumeric or backslash in preg_match_all.php on line 6
PHP Stack trace:
PHP   1. {main}() preg_match_all.php:0
PHP   2. preg_match_all($pattern = 'aeiou{0,', $subject = 'ou', $subpatterns = [0 => 'Orange', 1 => 'Apple', 2 => 'Banana', 3 => 'Monkey']) preg_match_all.php:6
preg_match_all.php:7:
bool(false)
preg_match_all.php:8:
array(4) {
    [0] =>
  string(6) "Orange"
    [1] =>
  string(5) "Apple"
    [2] =>
  string(6) "Banana"
    [3] =>
  string(6) "Monkey"
}
PHP Warning:  preg_match(): Delimiter must not be alphanumeric or backslash in preg_match_all.php on line 10
PHP Stack trace:
PHP   1. {main}() preg_match_all.php:0
PHP   2. preg_match($pattern = 'aeiou{0,', $subject = 'ou', $subpatterns = [0 => 'Orange', 1 => 'Apple', 2 => 'Banana', 3 => 'Monkey']) preg_match_all.php:10
preg_match_all.php:11:
bool(false)
preg_match_all.php:12:
array(4) {
    [0] =>
  string(6) "Orange"
    [1] =>
  string(5) "Apple"
    [2] =>
  string(6) "Banana"
    [3] =>
  string(6) "Monkey"
}

But I expected this output instead:

PHP Warning:  preg_match_all(): Delimiter must not be alphanumeric or backslash in preg_match_all.php on line 6
PHP Stack trace:
PHP   1. {main}() preg_match_all.php:0
PHP   2. preg_match_all($pattern = 'aeiou{0,', $subject = 'ou', $subpatterns = [0 => 'Orange', 1 => 'Apple', 2 => 'Banana', 3 => 'Monkey']) preg_match_all.php:6
preg_match_all.php:7:
bool(false)
preg_match_all.php:8:
either: null or array[0]
PHP Warning:  preg_match(): Delimiter must not be alphanumeric or backslash in preg_match_all.php on line 10
PHP Stack trace:
PHP   1. {main}() preg_match_all.php:0
PHP   2. preg_match($pattern = 'aeiou{0,', $subject = 'ou', $subpatterns = [0 => 'Orange', 1 => 'Apple', 2 => 'Banana', 3 => 'Monkey']) preg_match_all.php:10
preg_match_all.php:11:
bool(false)
preg_match_all.php:12:
either: null or array[0]

PHP Version

PHP 7.4.27

Operating System

No response

Reproduce the provided preg_match() and preg_match_all() calls with the invalid pattern on PHP 7.4.27, then trace the two APIs in the PHP interpreter. Done means a failed match no longer leaves the caller's previous $matches contents unchanged, with regression coverage for both functions.