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

Tái hiện các lệnh gọi preg_match() và preg_match_all() được cung cấp với mẫu không hợp lệ trên PHP 7.4.27, sau đó truy vết hai API trong trình thông dịch PHP. Hoàn tất có nghĩa là một lần khớp thất bại không còn giữ nguyên nội dung $matches trước đó của bên gọi, với độ bao phủ hồi quy cho cả hai hàm.