PHP常用的文件读写函数及操作方法

//打开或创建一个文件
$file = fopen("test.txt", "w+");

//写入文件
fwrite($file, "Hello World");

//读取文件
echo fread($file, filesize("test.txt"));

//关闭文件
fclose($file);

PHP连接数据库的方法

//连接数据库
$conn = mysqli_connect("localhost", "username", "password", "dbname");

//查询数据
$result = mysqli_query($conn, "SELECT * FROM users");

//取出结果集中的数据
while($row = mysqli_fetch_assoc($result)) {
  echo "Name: " . $row["name"] . " Age: " . $row["age"];
}

//关闭数据库连接
mysqli_close($conn);

PHP加密解密函数

//加密函数
function encrypt($str, $key) {
  $encrypted = base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, md5($key), $str, MCRYPT_MODE_CBC, md5(md5($key))));
  return $encrypted;
}

//解密函数
function decrypt($str, $key) {
  $decrypted = rtrim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, md5($key), base64_decode($str), MCRYPT_MODE_CBC, md5(md5($key))), "\0");
  return $decrypted;
}

//调用函数
$encrypted = encrypt("Hello World", "secretkey");
$decrypted = decrypt($encrypted, "secretkey");
echo $encrypted . " => " . $decrypted; //输出：RnplVjNXaXBMZmpWU3czc2QwckF5QT09 => Hello World