如果我试图在同一页面上发布答案，会是这样吗？不太确定我是否使用了正确的功能，请检查我的代码：
<form method="post" action="activity.php">
<input type="text" name= "num1" value="Enter a number"/>
<select name= "conversion">
<option>Select a conversion</option>
<option name="lb to kg">lbs to kgs</option>
<option name="kgs to lbs">kgs to lbs</option>
<option name="cm to in">cms to inchs</option>
<option name="inchs to cms">inchs to cms</option>
<option name="pints to litres">pints to litres</option>
<option name="litres to pints">litres to pints</option>
<option name="faranheit to centigrade">faranheit to centigrade</option>
<option name="centigrade ti faranheit">centigrade to faranheit</option>
</select>
<input type="submit" value="convert" />
</form>
然后php后面的表单：
$num1 = $_GET["num1"];
$conversion = $_POST["conversion"];
if($conversion == "lbs to kgs")
{
$answer_lb = $num1 * 0.45;
echo $answer_lb;
}
if($conversion == "kgs to lbs")
{
$answer_kg = $num1 * 2.2;
echo $answer_kg;
}
if($conversion == "cms to inchs")
{
$answer_inch = $num1 * 2.54;
echo $answer_inch;
}
if($conversion == "inchs to cms")
{
$answer_cm = $num1 * 0.393;
echo $answer_cm;
}
if($conversion == "pints to litres")
{
$answer_pints = $num1 * 0.568;
echo $answer_pints;
}
if($conversion == "litres to pints")
{
$answer_litres = $num1 * 1.579;
echo $answer_litres;
}
if($conversion == "faranheit to centigrade")
{
$answer_faranheit = ($num1 - 32) * (5/9);
echo $answer_faranheit;
}
if($conversion == "centigrade to faranheit")
{
$answer_centigrade = ($num1 * 9/5) + 32;
}
?>
<em>
我不确定php代码是否必须出现在表单之前或之后，也不确定表单的操作。
//根据您的需要编辑答案：
下面是一个代码的工作示例：http://codepad.viper-7.com/vu6j0N
<?php
$calculation_models = array();
$calculation_models[] = array('description'=>'lb to kg',
'calculation' => function($val) { return $val * 0.45; }
);
$calculation_models[] = array('description'=>'kgs to lbs',
'calculation' => function($val) { return $val * 2.2; }
);
$calculation_models[] = array('description'=>'cm to in',
'calculation' => function($val) { return $val * 2.54; }
);
$calculation_models[] = array('description'=>'inchs to cms',
'calculation' => function($val) { return $val * 0.393; }
);
$calculation_models[] = array('description'=>'pints to litres',
'calculation' => function($val) { return $val * 0.568; }
);
$calculation_models[] = array('description'=>'litres to pints',
'calculation' => function($val) { return $val * 1.579; }
);
$calculation_models[] = array('description'=>'faranheit to centigrade',
'calculation' => function($val) { return ($val - 32) * (5/9); }
);
$calculation_models[] = array('description'=>'centigrade to faranheit',
'calculation' => function($val) { return ($val * 9/5) + 32; }
);
if (isset($_GET['val']) && isset($_GET['model'])) {
$result = $calculation_models[$_GET['model']]['calculation']($_GET['val']);
echo 'The result is ' . $result;
}
?>
<!-- build the form dynamically from the array above -->
<form method="get" action="#">
<input type="text" name="val" placeholder="Enter a number"/>
<select name="model">
<?php foreach($calculation_models as $key => $model) : ?>
<option value="<?php echo $key; ?>"><?php echo $model['description']; ?></option>
<?php endforeach; ?>
</select>
<input type="submit" value="convert" />
</form>
如果你问这个问题，那么它并不简单。为了在不重新加载新页面的情况下改变页面的内容，通常涉及被称为AJAX的技术，基本上，它使用javascript提交请求，javascript将在收到响应后再次处理响应。
我认为您必须使用以下文件：calculator.html和calculator.php
calculator.html是形式.
使结果显示在同一页面上的第一个解决方案很简单：
像这个一样把所有东西都放进cacalculator.php
<?php
if($_GET["submit"]){
#your code
}
?>
<html>
<!-- your html -->
</html>
如果这不是您所要求的，那么下一个方法是使用iframe"with the result"和javascript将数据发送到iframe。
最后一个解决方案是简单的ajax。