<?= $gr->grp_name ?>
中的下划线替换空格 <div class="groupinfo">
<a href="<?= base_url() ?>group/group_id/<?= $gr->grp_id ?>/<?= $gr->grp_name ?>">
str_replace
替换下划线为空格<div class="groupinfo">
<a href="<?= base_url() ?>group/group_id/<?= $gr->grp_id ?>/<?= str_replace(" ","_",$gr->grp_name) ?>">
</div>