这个正则表达式怎么了?

为什么不直接使用str_replace()?我觉得比较简单

$search = "ab";
$word = "ameriabank";
$newstr = "<span class=\"pice1\">".str_replace($search, $word, "</span><span class=\"pice3\">".$search."</span></span class=\"pice1>\")."</span>";

$str = "i like programming very much";
$w = "r";
echo preg_replace("/($w)/", "<b>$1</b>", $str);

输出:

i like p<b>r</b>og<b>r</b>amming ve<b>r</b>y much

回答评论:分两步来做。

$str = "i like programming very much ready tear";
$w = "r";
$str = preg_replace("/\\b((?:\\w+|\\b)$w(\\w+|\\b))\\b/", "<i>$1</i>", $str);
$str = preg_replace("/($w)/", "<b>$1</b>", $str);
echo $str;

输出:

i like <i>p<b>r</b>og<b>r</b>amming</i> <i>ve<b>r</b>y</i> much <i><b>r</b>eady</i> <i>tea<b>r</b></i>

参观 highlight multiple keywords in search 并且感到惊讶。

$str = "i like programming very much";
$word = "r";
$list = explode(' ',$str);
for($i=0; $i<count($list); $i++) {
    if(preg_match("/$word/", $list[$i])) {
        $list[$i] = '<i>'.preg_replace("/$word/siu", "<b>$word</b>", $list[$i]).'</i>';
    }
}
$str = implode(' ',$list);
echo $str,"\n";

$str = "i like programming very much";
$word = "r";
function highlight($matches)
{
    global $word;
    return '<span class="pice1">'.str_replace($word,'<span class="pice2">'.$word.'</span>',$matches[0]).'</span>';
}
echo $str = preg_replace_callback("/([^\s]*?".preg_quote($word, '/')."[^\s]*)/siu", highlight, $str);

做这项工作(它也适用于外语)。。。