用PHP写一个 mysql数据库增删改查的全能类文件 和 使用示例

好的，下面是一个基本的 MySQL 数据库增删改查全能类的示例代码：

class MySQLDB {
    private $host;
    private $username;
    private $password;
    private $database;
    private $conn;

    public function __construct($host, $username, $password, $database) {
        $this->host = $host;
        $this->username = $username;
        $this->password = $password;
        $this->database = $database;
        $this->connect();
    }

    public function connect() {
        $this->conn = mysqli_connect($this->host, $this->username, $this->password, $this->database);
        if (!$this->conn) {
            die("Connection failed: " . mysqli_connect_error());
        }
    }

    public function query($sql) {
        $result = mysqli_query($this->conn, $sql);
        if (!$result) {
            die("Query failed: " . mysqli_error($this->conn));
        }
        return $result;
    }

    public function select($table, $columns = "*", $where = "") {
        $sql = "SELECT $columns FROM $table";
        if ($where != "") {
            $sql .= " WHERE $where";
        }
        return $this->query($sql);
    }

    public function insert($table, $data) {
        $columns = "";
        $values = "";
        foreach ($data as $column => $value) {
            $columns .= "$column,";
            $values .= "'$value',";
        }
        $columns = rtrim($columns, ",");
        $values = rtrim($values, ",");
        $sql = "INSERT INTO $table ($columns) VALUES ($values)";
        return $this->query($sql);
    }

    public function update($table, $data, $where = "") {
        $sql = "UPDATE $table SET ";
        foreach ($data as $column => $value) {
            $sql .= "$column='$value',";
        }
        $sql = rtrim($sql, ",");
        if ($where != "") {
            $sql .= " WHERE $where";
        }
        return $this->query($sql);
    }

    public function delete($table, $where = "") {
        $sql = "DELETE FROM $table";
        if ($where != "") {
            $sql .= " WHERE $where";
        }
        return $this->query($sql);
    }

    public function close() {
        mysqli_close($this->conn);
    }
}

这个类包含了连接数据库、执行 SQL 查询、插入数据、更新数据、删除数据和关闭连接的基本操作。使用示例代码如下：

$db = new MySQLDB("localhost", "root", "password", "mydatabase");
// 查询
$result = $db->select("mytable", "*", "id=1");
while ($row = mysqli_fetch_assoc($result)) {
    echo $row["column1"] . " " . $row["column2"] . "<br>";
}
// 插入
$data = array("column1" => "value1", "column2" => "value2");
$db->insert("mytable", $data);
// 更新
$data = array("column1" => "newvalue1", "column2" => "newvalue2");
$db->update("mytable", $data, "id=1");
// 删除
$db->delete("mytable", "id=1");
$db->close();

以上代码用于连接名为 `mydatabase` 的 MySQL 数据库，并执行查询、插入、更新和删除操作，最后关闭连接。您可以根据自己的需求修改这个类和使用示例代码。