妳要輸出什麽？我就假設兩個條件是數字，選好條件提交後，顯示條件1>還是<條件2吧。
<form?action=""?method="post"><label>條件1：
<select?name="select1">
<option?value="0"?selected="selected">選項1</option>
<option?value="1">選項2</option>
</select>
</label>
<label>?條件2：
<select?name="select2">
<option?value="0"?selected="selected">選項1</option>
<option?value="1">選項2option>
<option?value="2">選項3</option>
</select>
</label>
<input?name="b1"?type="submit"?value="查詢"?/>
<?php
if($_POST['select1']<$_POST['select2']){
echo?$_POST['select1']."<".$_POST['select2'];
}else?if($_POST['select1']>$_POST['select2']){
echo?$_POST['select1'].">".$_POST['select2'];
}
else?if($_POST['select1']=$_POST['select2']){
echo?$_POST['select1']."=".$_POST['select2'];
}
>