php如何连接字符串组成Sql语句

我做的是模糊查询，三个条件，

1不为空的话就select * from table where name like '%1%';

2不为空的话就select * from table where name like '%1%' and id=2;

3不为空的话就select * from table where name like '%1%' and content like '%3%';

如果都为空就select * from table；

php怎么拼接呢？

我不想那么多判断，麻烦。

<?php

$a = '';
$b = '';
$c = '';
$d = '';
$sql = "SELECt * from `table`";
if(!empty($a)) $sql = $sql."WHER `name` like '%1%'";
if(!empty($a))
{
if(!empty($b)) $sql = $sql."AND `id`='2'";
}else
{
if(!empty($b)) $sql = $sql."WHERe `id`='2'";
}
if(!empty($a))
{
if(!empty($c)) $sql = $sql."AND `content` like '%3%'";
}else
{
if(!empty($c)) $sql = $sql."WHERe `content` like '%3%'";
}
?>

$sql="select * from user where id in (1,2,3,4,5)"; if ($res=mysql_query($sql){ echo '<table>'; while ($row=mysql_fetch_row($res)){ echo '<tr><td>'; foreach ($row as $val) echo "<td>$val"; } echo '</table>'; } else echo "查询数据错误，SQL语句是:<BR>$SQL<BR>错误信息是:<BR>".mysql_error();