我有一个简单的编程练习，我正在尝试用PHP来做：确定学生是否通过了课程。如果学生三个年级的平均成绩大于或等于15分，他就会通过这门课程。如果学生通过或不通过，则显示一条消息，并在计算平均值之前验证三个成绩。如果分数有误，则显示错误消息。
我在伪代码和pseint中都有它，所以它很容易验证，因为我使用了一个do while循环，每次它要求我键入一个数字，而我做错了，它都会验证成绩：
Algorithm Exercise14
Define grade1, grade2, grade3, prom as Real;
Repeat
print "Type the first grade: ";
read grade1;
if (grade1<0 | grade1>20)
print "Error! Invalid grade, type a valid grade.";
endif
Until (grade1>=0 & grade2<=20);
Repeat
print "Type the second grade: ";
read grade2;
if (grade2<0 | grade2>20)
print "Error! Invalid grade, type a valid grade.";
endif
Until (grade2>=0 & grade2<=20);
Repeat
print "Type the third grade: ";
read grade3;
if (grade3<0 | grade3>20)
print "Error! Invalid grade, type a valid grade.";
endif
Until (grade3>=0 & grade3<=20);
prom = (grade1+grade2+grade3)/3;
if (prom>=15)
print "The student passed the course!";
print "The average is: " prom;
else
print "The student did not pass the course.";
print "The average is: " prom;
endif
endAlgorithm
现在，我想用PHP来做这件事。我的问题是，我不能用这种方式进行验证，因为如果我这样做，浏览器只需要花很多时间来做出反应，它什么也不做，所以我在互联网上看了看，我需要一些功能来验证，但我不确定。我正在学习PHP，所以，如果这是一个重复的问题，或者很容易，请原谅，但我想知道，因为我正在学习。
最后一个问题是，如果我使用PHP，显然还有HTML5，我如何验证这些字段？
PHP代码：
<!DOCTYPE html>
<html lang="en">
<head>
<title>Exercise 14</title>
<meta charset="utf-8">
</head>
<body>
<h2>PHP Exercises</h2>
<h3>Exercise 14</h3>
<form action="#" method="post" id="constant" name="constant">
<div>
<label for="text">Grade 1: </label>
<input type="text" name="grade1" placeholder="Type grade1">
</div>
<div>
<label for="text">Grade 2: </label>
<input type="text" name="grade2" placeholder="Type grade 2">
</div>
<div>
<label for="text">Grade 3: </label>
<input type="text" name="grade3" placeholder="Type grade 3">
</div>
<div>
<input type="submit" name="button" id="sending" value="Send">
</div>
</form>
<?php
if(isset($_POST['button'])){
$grade1 = $_POST['grade1'];
$grade2 = $_POST['grade2'];
$grade3 = $_POST['grade3'];
while($grade1<0){
echo "Error!";
}
do{
if ($grade2<0 | $grade2>20) {
echo "Error!";
}
}while($grade2>=0 && $grade2<=20);
do{
if ($grade3<0 | $grade3>20) {
echo "Error!";
}
}while($grade3>=0 && $grade3<=20);
$prom = ($grade1+$grade2+$grade3/3);
if ($prom>=15) {
echo "The averages is: " . $prom;
echo "The student passed the course!";
}else{
echo "The averages is: " . $prom;
echo "The student did not pass the course.";
}
}
?>
</body>
</html>
PHP无法从命令提示符或其他立即刷新的输入中进行交互读取。为web客户端编写服务器端代码的模式始终是，web客户端（浏览器、HTML）发送一个包含数据的HTTP请求，服务器评估该数据，然后发送响应。在发出另一个HTTP请求之前，数据不会刷新。因此，在$_POST值上循环直到它是正确的值是没有意义的；在一次代码执行过程中，该值不会改变。你的逻辑必须是：
- 对每个输入进行一次评估
- 如果任何一个输入无效，则拒绝整个请求
- 只有在所有输入都有效的情况下，才可以执行您想要执行的操作
- 返回一个HTML响应，说明错误或成功之处
示例免费：
<?php
$errors = [];
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
if ($_POST['grade1'] < 0) {
$errors['grade1'] = 'Too low';
}
...
if (!$errors) {
// validation successful, do something
}
}
?>
<form method="post">
<input name="grade1" value="<?= htmlspecialchars($_POST['grade1'] ?? null); ?>">
<?php if (isset($errors['grade1'])) : ?>
<span class="error"><?= $errors['grade1']; ?></span>
<?php endif; ?>
...
</form>
<!DOCTYPE html>
<html lang="en">
<head>
<title>Exercise 14</title>
<meta charset="utf-8">
</head>
<body>
<h2>PHP Exercises</h2>
<h3>Exercise 14</h3>
<form name="exer14" action="#" method="post" id="constant" name="constant">
<div>
<label for="text">Grade 1: </label>
<input type="number" name="grade1" placeholder="Type grade 1" required>
</div>
<div>
<label for="text">Grade 2: </label>
<input type="number" name="grade2" placeholder="Type grade 2" required>
</div>
<div>
<label for="text">Grade 3: </label>
<input type="number" name="grade3" placeholder="Type grade 3" required>
</div>
<div>
<input type="submit" name="button" id="sending" value="Send">
</div>
</form>
<?php
if(isset($_POST['button'])){
$grade1 = $_POST['grade1'];
$grade2 = $_POST['grade2'];
$grade3 = $_POST['grade3'];
$count = 0;
$errors = array("Error1" => "Error! The grade $grade1 is invalid. Type a grade between 0 and 20.",
"Error2" => "Error! The grade $grade2 is invalid. Type a grade between 0 and 20.",
"Error3" => "Error! The grade $grade3 is invalid. Type a grade between 0 and 20.");
if (empty($_POST['grade1']) || empty($_POST['grade2']) || empty($_POST['grade3'])) {
echo "Complete all inputs.";
}elseif (is_numeric($grade1)==false || is_numeric($grade2)==false || is_numeric($grade3)==false) {
if (is_numeric($grade1)==false) {
echo "Error! Invalid grade: '$grade1' contains letters. Type a grade between 0 and 20." . "<br>";
}
if (is_numeric($grade2)==false) {
echo "Error! Invalid grade: '$grade2' contains letters. Type a grade between 0 and 20." . "<br>";
}
if (is_numeric($grade3)==false) {
echo "Error! Invalid grade: '$grade3' contains letters. Type a grade between 0 and 20." . "<br>";
}
}elseif ($grade1<0 || $grade1>20 || $grade2<0 || $grade2>20 || $grade3<0 || $grade3>20) {
if ($grade1<0 || $grade1>20){
echo $errors["Error1"] . "<br>";
}
if ($grade2<0 || $grade2>20){
echo $errors["Error2"] . "<br>";
}
if ($grade3<0 || $grade3>20){
echo $errors["Error3"] . "<br>";
}
//print_r($errors);
}elseif (($grade1>=0 || $grade1<=20) && ($grade2>=0 || $grade2<=20) && ($grade3>=0 || $grade3<=20)) {
$prom = ($grade1+$grade2+$grade3)/3;
if ($prom>=15) {
echo "The student average is " . $prom . "<br>";
echo "The student passed the course!";
}else{
echo "The student average is " . $prom . "<br>";
echo "The student failed the course.";
}
}else{
echo "Enter the right grades.";
}
}
?>
</body>
我已经用这种方法解决了这个问题。我可以用几个大小写、字母和数字范围来验证这些输入。这个练习真的很简单，但我是在Pseint和C++中完成的，所以它们与PHP非常不同。我现在明白了服务器客户端是关于什么的。