PHP learning experience: How to write secure code

PHP Learning Experience: How to Write Secure Code

In the Internet era, with the rapid development of information, network security has become an increasingly important issue. As a developer who is learning PHP, writing secure code is our unshirkable responsibility. This article will share some insights on how to write secure PHP code, along with some code examples.

1. Input validation
   Input validation is the first step in writing secure code. Any data obtained from user input needs to be validated to prevent malicious users from submitting malicious data. Here is a simple example that demonstrates how to verify a mobile number:

function validatePhoneNumber($phoneNumber) {
   $pattern = "/^[1-9]d{10}$/";
   if (preg_match($pattern, $phoneNumber)) {
      // 验证通过，继续处理逻辑
   } else {
      // 验证失败，给出错误提示
   }
}

2. Output filtering
   Be sure to filter the data before outputting it to the front-end page. This ensures that malicious scripts submitted by users will not be executed and avoids XSS (cross-site scripting attacks) vulnerabilities. Here is a simple output filtering example:

function filterOutput($string) {
   return htmlspecialchars($string, ENT_QUOTES, 'UTF-8');
}

// 输出到前端页面
echo filterOutput($userInput);

3. Database Security
   Passing user input directly to a database query is very dangerous and vulnerable to SQL injection attacks. To avoid this situation, you can use prepared statements and parameter binding to process database queries and protect the security of the database. The following is an example of using prepared statements and parameter binding:

$pdo = new PDO("mysql:host=localhost;dbname=myDatabase", "username", "password");

$statement = $pdo->prepare("SELECT * FROM users WHERE username = :username AND password = :password");
$statement->bindParam(':username', $username);
$statement->bindParam(':password', $password);

$statement->execute();

$result = $statement->fetch(PDO::FETCH_ASSOC);

4. File upload
   The file upload function is a commonly used function, but it is also a potential security risk. Reasonable restrictions should be placed on uploaded files, including file type, file size, etc., to ensure that users cannot upload malicious files or huge files that occupy server resources. The following is an example of file upload:

if ($_FILES["file"]["size"] > 2000000) {
   echo "文件过大";
   exit;
}

$allowedFileType = array("pdf", "doc", "jpg", "png");
$allowedFileSize = 500000;

$uploadedFileType = strtolower(pathinfo($_FILES["file"]["name"], PATHINFO_EXTENSION));
if (!in_array($uploadedFileType, $allowedFileType)) {
   echo "不支持的文件类型";
   exit;
}

if ($_FILES["file"]["size"] > $allowedFileSize) {
   echo "文件过大";
   exit;
}

// 保存上传文件
move_uploaded_file($_FILES["file"]["tmp_name"], "uploads/" . $_FILES["file"]["name"]);

By paying attention to the above aspects, we can greatly improve our ability to write secure PHP code and protect user data and system security. Of course, these are just some basic security measures. We also need to continue to learn and pay attention to the latest security technologies to deal with evolving network security threats. I hope these insights will be helpful to developers who are learning PHP.

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