如何爲不同的選擇操作編寫助手類？

Question

夥計們我想根據我的需要選擇不同的操作，但我只需要一個輔助函數來執行所有選擇操作，我如何得到它？

這是我的助手類database.php中

<?php 
class Database 
{ 
    public $server = "localhost"; 
    public $user = "root"; 
    public $password = ""; 
    public $database_name = "employee_application"; 
    public $table_name = ""; 
    public $database_connection = ""; 
    public $class_name = "Database"; 
    public $function_name = ""; 
    //constructor 
    public function __construct(){ 
    //establishes connection to database 
     $this->database_connection = new mysqli($this->server, $this->user, $this->password, $this->database_name); 
     if($this->database_connection->connect_error) 
      die ("Connection failed".$this->database_connection->connect_error); 
    } 
    //destructor 
    public function __destruct(){ 
    //closes database connection 
     if(mysqli_close($this->database_connection)) 
     { 
      $this->database_connection = null; 
     } 
     else 
      echo "couldn't close"; 
    } 

    public function run_query($sql_query) 
    { 
     $this->function_name = "run_query"; 
     try{ 
      if($this->database_connection){ 
       $output = $this->database_connection->query($sql_query); 
       if($output){ 
        $result["status"] = 1; 
        $result["array"] = $output; 
       } 
       else{ 
        $result["status"] = 0; 
        $result["message"] = "Syntax error in query"; 
       } 
      } 
      else{ 
       throw new Exception ("Database connection error"); 
      } 
     } 
     catch (Exception $error){ 
      $result["status"] = 0; 
      $result["message"] = $error->getMessage(); 
      $this->error_table($this->class_name, $this->function_name, "connection error", date('Y-m-d H:i:s')); 
     } 
     return $result; 
    } 
    public function get_table($start_from, $per_page){ 
     $this->function_name = "get_table"; 
     $sql_query = "select * from $this->table_name LIMIT $start_from, $per_page"; 
     return $this->run_query($sql_query); 
    } 
} 
?> 

在上面的代碼get_table功能進行基本的選擇操作.... 現在我想get_table函數來執行這一切操作之下，

$sql_query = "select e.id, e.employee_name, e.salary, dept.department_name, desi.designation_name, e.department, e.designation 
             from employees e 
             LEFT OUTER JOIN designations desi ON e.designation = desi.id 
             LEFT OUTER JOIN departments dept ON e.department = dept.id 
             ORDER BY e.employee_name 
             LIMIT $start_from, $per_page"; 


$sql_query = "select id, designation_name from designations ORDER BY designation_name"; 
$sql_query = "select * from departments"; 
$sql_query = "select * from departments Limit 15,10"; 

那麼如何解決這個問題，誰能幫我解決？

Answer 1

如果你擴展你的班級，你可以實現你正在尋找的東西。事情是這樣的：

<?php 
    class Database 
     { 
      public  $sql; 
      public  $bind; 
      public  $statement; 
      public  $table_name; 

      protected $orderby; 
      protected $set_limit; 
      protected $function_name; 
      protected $sql_where; 
      protected $i; 

      protected function reset_class() 
       { 
        // reset variables 
        $this->sql    = array(); 
        $this->function_name = false; 
        $this->table_name  = false; 
        $this->statement  = false; 
        $this->sql_where  = false; 
        $this->bind    = array(); 
        $this->orderby   = false; 
        $this->set_limit  = false; 
       } 

      protected function run_query($statement) 
       { 
        echo (isset($statement) && !empty($statement))? $statement:""; 
       } 

      public function get_table($start_from = false, $per_page = false) 
       { 
        // Compile the sql into a statement 
        $this->execute(); 
        // Set the function if not already set 
        $this->function_name = (!isset($this->function_name) || isset($this->function_name) && $this->function_name == false)? "get_table":$this->function_name; 
        // Set the statement 
        $this->statement  = (!isset($this->statement) || isset($this->statement) && $this->statement == false)? "select * from ".$this->table_name:$this->statement; 

        // Add on limiting 
        if($start_from != false && $per_page != false) { 
          if(is_numeric($start_from) && is_numeric($per_page)) 
           $this->statement .= " LIMIT $start_from, $per_page"; 
         } 

        // Run your query 
        $this->run_query($this->statement); 
        // Reset the variables 
        $this->reset_class(); 

        return $this; 
       } 

      public function select($value = false) 
       { 
        $this->sql[] = "select"; 

        $this->function_name = "get_table"; 

        if($value != false) { 
          $this->sql[] = (!is_array($value))? $value:implode(",",$value); 
         } 
        else 
         $this->sql[] = "*"; 

        return $this; 
       } 

      public function from($value = false) 
       { 
        $this->sql[] = "from"; 
        $this->sql[] = "$value"; 

        return $this; 
       } 

      public function where($values = array(), $not = false, $group = false,$operand = 'and') 
       { 

        if(empty($values)) 
         return $this; 

        $this->sql_where = array(); 

        if(isset($this->sql) && !in_array('where',$this->sql)) 
         $this->sql[]  = 'where'; 

        $equals    = ($not == false || $not == 0)? "=":"!="; 

        if(is_array($values) && !empty($values)) { 
          if(!isset($this->i)) 
           $this->i = 0; 


          foreach($values as $key => $value) { 

            $key = trim($key,":"); 


            if(isset($this->bind[":".$key])) { 
              $auto = str_replace(".","_",$key).$this->i; 
             // $preop = $operand." "; 
             } 
            else { 
             // $preop = ""; 
              $auto = str_replace(".","_",$key); 
             } 

            $this->bind[":".$auto] = $value; 
            $this->sql_where[]  = $key." $equals ".":".$auto; 
            $this->i++; 
           } 

          if($group == false || $group == 0) 
           $this->sql[] = implode(" $operand ",$this->sql_where); 
          else 
           $this->sql[] = "(".implode(" $operand ",$this->sql_where).")"; 
         } 
        else { 
          $this->sql[]  = $values; 
         } 

        if(is_array($this->bind)) 
         asort($this->bind); 

        return $this; 
       } 

      public function limit($value = false,$offset = false) 
       { 
        $this->set_limit  = ""; 

        if(is_numeric($value)) { 

          $this->set_limit  = $value; 

          if(is_numeric($offset)) 
           $this->set_limit = $offset.", ".$this->set_limit; 
         } 

        return $this; 
       } 

      public function order_by($column = array()) 
       { 
        if(is_array($column) && !empty($column)) { 
          foreach($column as $colname => $orderby) { 
            $array[] = $colname." ".str_replace(array("'",'"',"+",";"),"",$orderby); 
           } 
         } 
        else 
         $array[] = $column; 

        $this->orderby = implode(", ",$array); 

        return $this; 
       } 

      public function execute() 
       { 
        $limit    = (isset($this->set_limit) && !empty($this->set_limit))? " LIMIT ".$this->set_limit:""; 
        $order    = (isset($this->orderby) && !empty($this->orderby))? " ORDER BY ".$this->orderby:""; 

        $this->statement = (is_array($this->sql))? implode(" ", $this->sql).$order.$limit:""; 

        return $this; 
       } 

      public function use_table($table_name = 'employees') 
       { 
        $this->table_name = $table_name; 
        return $this; 
       } 
     } 

使用方法：

// Create instance 
    $query = new Database(); 

    // Big query 
    $query ->select(array("e.id", "e.employee_name", "e.salary", "dept.department_name", "desi.designation_name", "e.department", "e.designation")) 
      ->from("employees e LEFT OUTER JOIN designations desi ON e.designation = desi.id LEFT OUTER JOIN departments dept ON e.department = dept.id") 
      ->order_by(array("e.employee_name"=>"")) 
      ->limit(1,5)->get_table(); 

    // More advanced select 
    $query ->select(array("id", "designation_name")) 
      ->from("designations") 
      ->order_by(array("designation_name"=>"")) 
      ->get_table(); 

    // Simple select 
    $query ->use_table("departments") 
      ->get_table(); 

    // Simple select with limits 
    $query ->use_table("departments") 
      ->get_table(10,15); 

?> 

爲您提供：

// Big query 
select e.id,e.employee_name,e.salary,dept.department_name,desi.designation_name,e.department,e.designation from employees e LEFT OUTER JOIN designations desi ON e.designation = desi.id LEFT OUTER JOIN departments dept ON e.department = dept.id ORDER BY e.employee_name LIMIT 5, 1 

// More advanced select 
select id,designation_name from designations ORDER BY designation_name 

// Simple select 
select * from departments 

// Simple select with limits 
select * from departments LIMIT 10, 15