<?php $txt='[div=back]我是UBB[/div]'; $txt=preg_replace('!\[div=(.*?)\](.*?)\[/div\]!','<div class="$1">$2</div>',$txt); echo $txt; ?>
<?php $txt='[[empty]div=back]我是UBB[[empty]/div]'; $txt=preg_replace('!\[div=(.*?)\](.*?)\[/div\]!','<div class="$1">$2</div>',$txt); echo $txt; ?>
<?php $txt='[[empty]div=back]我是UBB[[empty]/div]'; $txt=preg_replace('!\[[empty]div=(.*?)\](.*?)\[[empty]/div\]!','<div class="$1">$2</div>',$txt); echo $txt; ?>