PHP中preg_match()和preg_match_all()正则表达式的用法区别

<?php
if(preg_match("/php/i", "PHP is the web scripting language of choice.", $matches)){
    print "A match was found:". $matches[0];
} else {
    print "A match was not found.";
}
?>
A match was found: PHP

<?php
// 从 URL 中取得主机名
preg_match("/^(http://)?([^/]+)/i","https://www.mdaima.com/jingyan/", $matches);
$host = $matches[2];
// 从主机名中取得后面两段
preg_match("/[^./]+\.[^./]+$/", $host, $matches);
echo "域名为：{$matches[0]}";
?>
域名为：jb51.net

$get_htm_hello='<div class="information-details-msg">
                    <span class="send-time">发布时间：<span>2023-02-09 09:17:17</span></span>
                    <span class="comefrom">来源：<span>李雷博客</span></span>
                    <span class="readmath">阅读：<span id="reading_quantity">5899</span></span>
                    <span class="send-time">发布时间：<span>2023-02-10 09:17:17</span></span>
                    <span class="special">栏目：<a style="color:#9EA7B3;" href="https://www.mdaima.com"><span>PHP博客</span></a></span>';


$fabutime_regex_1 =  '/发布时间：<span>.*<\/span><\/span>/i';
preg_match_all($fabutime_regex_1, $get_htm_hello, $fabutime_array);
$fabutime = $fabutime_array[0];
$fabutime = str_replace('发布时间：<span>', '', $fabutime);
$fabutime = str_replace('</span></span>', '', $fabutime);

print_r($fabutime);
echo $fabutime[0];
exit;

<?php
$str = "学习php是一件快乐的事。";
preg_match_all("/[x80-xff]+/", $str, $match);
//UTF-8 使用：
//preg_match_all("/[x{4e00}-x{9fa5}]+/u", $str, $match);
print_r($match);
?>

Array
(
    [0] => Array
        (
            [0] => 学习
            [1] => 是一件快乐的事。
        )
)