试图使用php和html代码向mysql数据库添加新列，但是代码不起作用，只是在Safari浏览器中出现白页，Chrome浏览器告诉我
此页面无法正常运行localhost当前无法处理此请求。HTTP错误500
我正在使用MAMP /Applications/MAMP/bin/php/php7.4.1/bin/php-cgi -e -b 127.0.0.1:49949
home.html代码：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<form action="data.php" method="post">
<h2>newdata</h2>
<label>enter data:</label>
<input type="text" name="nclm" >
<input type="submit" name="newdata" value="newdata">
</form>
</body>
</html>
database.php
<?php
$servername='127.0.0.1';
$username='root';
$password='12345678';
$dbname = "company";
$conn=mysqli_connect($servername,$username,$password,"$dbname");
if(!$conn){
die('Could not Connect My Sql:' .mysql_error());
}
?>
data.php
<?php
include_once 'database.php';
if(isset($_POST['newdata'])) {
$nclm = $_POST['nclm'];
$added = mysql_query("ALTER TABLE employees ADD .'$nclm'. VARCHAR(50) NOT NULL ");
if ($added !== FALSE) {
echo("The column has been added.");
} else {
echo("The column has not been added.");
}
}
?>