PHP（静态？）数据库帮助程序类

Question

[在最近的一个有趣的项目（用于管理账单和客户的系统中，我决定使用PDO作为数据库接口。我遇到了一个问题，就是在使用准备好的语句（准备，设置参数，执行等）时，我一直在编写相同的代码，因此我决定编写一个小助手类，其中包含使用速度更快的方法（select，selectRow，等）。

我知道这不是最佳选择，而且PDO本身已经“足够好”（我已经阅读了有关PDO助手类的其他问题），但是我的问题更多地涉及使用（静态）助手类时的常规设计。 ！

这里是我的第一种方法的代码

class DBA {
  private $con;

  public function __construct () {
     $this->con = new PDO ( .. );
  }

  public function select ($query, $params = array()) {
     $sth = $this->con->prepare($query);
     ....
  }

  // returns an object
  public function fetchObject ($query, $params = array(), $class) {
    $sth = $this -> con -> prepare($query);
    $sth -> setFetchMode(PDO::FETCH_CLASS, $class);
    ..
  }
 ...
}

class Bill {
    public $date;
    public $payed;
    // ...

    public function markAsPayed () {
      $dba = new DBA();
      if($dba -> exec ('UPDATE ..', $args)) {
         return true,
      }
      return false;
    }
}

// index.php
$dba = new DBA ();
$bill = $dba -> fetchObject ('SELECT ..', $args, 'Bill');
$bill -> markAsPayed();

我发现了以下问题：我通过创建类的实例在其他类中使用该类（例如，在从数据库行中获取的对象中）。因此，将有大量的辅助类实例（这意味着大量的连接），因为我正在使用辅助类的其他类的每个方法中创建一个实例。当我调用使用helper类的方法时，在由helper类创建的对象上，整个应用程序变得非常慢。

将助手类设为静态是一个好的解决方案吗？如果是这样，我如何连接到数据库？我应该使用单例模式吗？我不想在helper类的每个方法中都重新连接到数据库，但是在helper类中具有全局连接。

Answer 1

您需要这样的课程：

class DataBase {
	
	public $conn;
	
	public $queryCount = 0;
	
	public $queries = array();
	
	static private $instance;
	
	public function __construct()
	{
		$this->conn = mysqli_connect(DB_HOST, DB_USER, DB_PASSWORD);
		mysqli_select_db($this->conn, DB_NAME);
		mysqli_set_charset($this->conn, 'utf8');
	}
	
	static public function instance()
	{
		if (!isset(self::$instance)) {
			$name = __CLASS__;
			self::$instance = new $name;
		}
		return self::$instance;
	}
	
	public function esc($str)
	{  
		if (is_null($str)) return null; 
		return mysqli_real_escape_string($this->conn, $str); 
	}
	public function escape($str)
	{ 
		if (is_null($str)) return null; 
		return mysqli_real_escape_string($this->conn, $str); 
	} 
	
	public function escapeArray($arr)
	{
        foreach ($arr as $k => $v) {
        	if (!is_null($v)) {
            	$arr[$k] = $this->escape($v);
            }
        }
        return $arr;
	}
	
	public function lastError() {
		return mysqli_error($this->conn);
	}
	public function query($query)
	{
		$this->queryCount++;
		$this->queries[] = $query;
		
		$result = mysqli_query($this->conn, $query);
		
		if ($result === false) {
			$this->debug($query);
		}
		
		if (mysqli_num_rows($result) == 0) {
			return array();
		}
		
		$salida = array();
		while ($row = mysqli_fetch_assoc($result)) {
			$salida[] = $row;
		}
		mysqli_free_result($result);
		
		return $salida;
	}
	
	public function count($table, $opts = array())
	{
		$where = "";
		
		if (!empty($opts['where'])) {
			$where = $this->where($opts['where']);
		}
		
		$query = "SELECT COUNT(*) AS result FROM $table $where";
		
		$row = $this->queryOne($query);
		
		return (int)$row['result'];
	}
	
	public function lastId()
	{
		return mysqli_insert_id($this->conn);
	}
	
	protected function debug($query)
	{
		//echo "<br>Error in the sentence: ". $query . "<br>";
		//echo mysqli_error();
		//$e = new Exception();
		//pr($e->getTraceAsString());
	}
	
	public function insert($table, $data)
	{
		$this->queryCount++;
		
		$fields = $this->escapeArray(array_keys($data));
		$values = $this->escapeArray(array_values($data));
		
		foreach ($values as $k => $val) {
			if (is_null($val)) {
				$values[$k] = 'NULL';
			} else {
				$values[$k] = "'$val'";
			}
		}
		
		$query = "INSERT INTO $table(`".join("`,`",$fields)."`) VALUES(".join(",", $values).")";
		
		$this->queries[] = $query;
		
		return mysqli_query($this->conn, $query);
	}
	
	public function execute($query)
	{
		$this->queryCount++;
		$this->queries[] = $query;
		
		return mysqli_query($this->conn, $query);
	}
	public function multiExecute($multiQuery)
	{
		$this->queryCount++;
		$this->queries[] = $multiQuery;
		
		return mysqli_multi_query($this->conn, $multiQuery);
	}
	
	public function getAffectedRows()
	{
		return mysqli_affected_rows($this->conn);
	}
	
	public function select($table, $opts = array())
	{
		$fields = "*";
		$where = '';
		$order = '';
		
		if (!empty($opts['fields'])) {
			if (is_array($opts['fields'])) {
				$fields = join(",", $opts['fields']);
			} else {
				$fields = $opts['fields'];
			}
		}
		
		if (!empty($opts['where'])) {
			$where = $this->where($opts['where']);
		}
		
		if (!empty($opts['order'])) {
			$order = "ORDER BY " . $opts['order'];
		}
		
		$query = "SELECT $fields FROM $table $where $order";
		
		if (!empty($opts['limit'])) {
			if ($opts['limit'] === 1 || $opts['limit'] == '1') {
				return $this->queryOne($query." LIMIT 1");
			}
			
			$query .= " LIMIT ".$opts['limit'];
		}
		
		return $this->query($query);
	}
	
	public function selectOne($table, $opts = array())
	{
		$opts['limit'] = 1;
		return $this->select($table, $opts);
	}
	
	public function update($table, $data, $opts = array())
	{
		$where = "";
		if (!empty($opts['where'])) {
			$where = $this->where($opts['where']);
		}
		
		$update = array();
		foreach ($data as $field => $value) {
			if (is_null($value)) {
				$update[] = "`$field` = NULL";
			} else {
				$update[] = "`$field` = '".$this->esc($value)."'";
			}
		}
		
		$query = "UPDATE $table SET ".join(" , ", $update)." $where";
		
		return $this->execute($query);
	}
	}

请参阅here以获取完整的课程