表单使用函数计算BMI并显示不同的注释.致命错误，显示不正确 - Form using function calculate BMI and display different comment. Fatal error and not displaying correctly

Form using function calculate BMI and display different comment. Fatal error and not displaying correctly

我正在创建一个使用函数计算BMI的表单。两个问题。

注释（体重不足/正常体重/…）的输出应根据计算出的BMI而有所不同，但无论BMI值是多少，它总是输出underweight。我需要做什么才能让它工作？

"致命错误：调用…中未定义的函数bmi（）"尽管该函数有效，但仍显示致命错误。有人能教我如何摆脱这个错误吗？非常感谢。

<form name="bmi" method="GET" action="test.php">
  Mass in kilogram (kg):
  <input type="text" name="mass" id="mass" size="15">
  <br> 
  Height in meter (m):
  <input type="text" name="height" id="height" size="15">
  <br>
  <input type="submit" name="submit" id="submit" value="submit">
</form>
<?php
if ($_GET['submit']) { 
  $mass = $_GET['mass'];
  $height = $_GET['height'];
  function bmi($mass,$height) {
    $bmi = $mass/($height*$height);
    return $bmi;
  } 
  if ($bmi <= 18.5) {
    $output = "UNDERWEIGHT";
  } else if ($bmi > 18.5 AND $bmi<=24.9 ) {
    $output = "NORMAL WEIGHT";
  } else if ($bmi > 24.9 AND $num<=29.9) {
    $output = "OVERWEIGHT";
  } else if ($bmi > 30.0) {
    $output = "OBESE";
  }
}
echo "Your BMI value is  " . bmi($mass,$height). "  and you are : "; 
echo "$output";
?>

您需要在if子句之前使用函数：

if ($_GET['submit']) { 
    $mass = $_GET['mass'];
    $height = $_GET['height'];
    function bmi($mass,$height) {
        $bmi = $mass/($height*$height);
        return $bmi;
    }   
    $bmi = bmi($mass,$height); //<--- this is critical
    if ($bmi <= 18.5) {
        $output = "UNDERWEIGHT";
        } else if ($bmi > 18.5 AND $bmi<=24.9 ) {
        $output = "NORMAL WEIGHT";
        } else if ($bmi > 24.9 AND $bmi<=29.9) {
        $output = "OVERWEIGHT";
        } else if ($bmi > 30.0) {
        $output = "OBESE";
    }
    echo "Your BMI value is  " . $bmi . "  and you are : "; 
    echo "$output";
}

您的$输出始终相同，因为您的IF语句永远不会运行。U必须在IF语句之前设置$bmi变量的某个值，这样就可以添加IF语句之前的$bmi = bmi($mass, $height)，然后在echo命令中调用bmi函数，您可以使用$bmi变量

<?php
if ($_GET['submit']) { 
    $mass = $_GET['mass'];
    $height = $_GET['height'];
    $height2 = ($height*$height);
    $bmi = $mass/$height2; //<--- this is critical
    if ($bmi <= 18.5) {
        $output = "UNDERWEIGHT";
        } else if ($bmi > 18.5 AND $bmi<=24.9 ) {
        $output = "NORMAL WEIGHT";
        } else if ($bmi > 24.9 AND $bmi<=29.9) {
        $output = "OVERWEIGHT";
        } else if ($bmi > 30.0) {
        $output = "OBESE";
    }
    echo "Your BMI value is  " . $bmi . "  and you are : "; 
    echo "$output";
}
?>