怎么在网页上用PHP做个搜索功能？

通过from表单，将查询的关键词，通过 like 跟数据进行模糊查询对比

从topics表中查询字段subject与传进来的参数'$_POST['topic']进行比较模糊查询

设subject字段数据为：数学，英语，物理，化学，英文

$subject=$_POST['topic'];

$sql = "select * from topics where subject like '%" .$subject. "%'";

$result = mysql_query($sql);

若从表单提交的‘topic’值为“学”，得到的结果将是：数学，化学

多个字段匹配查询：

$sql = "select id,subject from topics where (id like '%" .$id. "%') or (name like '%" .$name. "%') or (subject like '%" .$subject. "%') order by id desc";

结果依据字段id的顺序