求助一个正则表达式的问题

Question

我想写一个正则表达式,
{protect}
{aa}
{/protect}
{aa}只替换未受{protect}保护的{aa}元素为abc 
可以实现吗？

Answer 1

<?php
$str='{protect}
{aa}
{/ptotect}
{aa}';
echo preg_replace("/(?<!{protect})\s*{aa}\s*(?!{\/protect})/",'111',$str);
?>

Answer 2

$str = <<<template
{protect}
{aa}
{/protect}
{aa} 
template;
$str = preg_replace("/\{protect\}(.*)\{\/protect\}/iseu",'str_replace("{aa}","abc","\\0")',$str);
echo $str;

Answer 3

不知道是不是LZ的意思  $a = '{aa}{protect} 
{aa} 
{/protect} 
{aa}{protect} 
{aa} 
{/protect} 
{aa}';
   
   echo preg_replace('/({\/protect}[^\/{}]*|^[^\/{}]*){aa}([^\/{}]*{protect}|[^\/{}]*$)/is','${1}123$2',$a);

Answer 4

$str = <<<template
{protect}
{aa} {aa}
{/protect}
{aa} {aa}
template;echo preg_replace("#(\{protect\}.*\{\/protect\}|\{aa\})#ise",'preg_replace("#^{aa}$#","abc","\\0")',$str);

Answer 5

有规律就可以吧
<?php
$str='
{aa} 
{protect} 
{aa} 
{/protect} 
{aa} 
';
$reg='/\{aa\}(?![^{]*\{\/protect\})/iU';
$str = preg_replace($reg, 'abc', $str);
echo $str;
?>