How to replace specified characters in php regular variables

<?php
$str = preg_quote(&#39;(银子)&#39;);
$txt = &#39;我的呢称(银子)&#39;;
echo preg_replace("/($str)/","<span style=&#39;color:#f00;&#39;>$1</span>",$txt);
?>

<?php
$str = quotemeta(&#39;(银子)&#39;);
$txt = &#39;我的呢称(银子)&#39;;
echo preg_replace("/($str)/","<span style=&#39;color:#f00;&#39;>$1</span>",$txt);
?>

<?php
$str = &#39;(银子)&#39;;
$txt = &#39;我的呢称(银子)&#39;;
echo preg_replace("/(Q$strE)/","<span style=&#39;color:#f00;&#39;>$1</span>",$txt);
?>

$text = "foobar123fooabcbar";
$text = preg_replace("/foo(?=bar)/", "***", $text);
//匹配bar前面的位置 ***bar123fooabcbar

$text = "foobar123fooabcbar";
$text = preg_replace("/(?<=bar)123/", "***", $text);
//匹配bar后面的位置 foo***123fooabcbar

$text = "foobar123fooabcbar";
$text = preg_replace("/foo(?!bar)/", "***", $text);
//匹配后面跟的不是bar的位置    foobar123***abcbar

$text = "foobar123fooabcbar";
$text = preg_replace("/(?<!foo)bar/", "***", $text);
//匹配前面不是foo的位置 foobar123fooabc***