使用 PHP OOP 连接到数据库

Question

I am developing PHP OOP application, which I need help with. I am developing a class(fetch_assoc) which has a function db_connect. It simply connects to the database. Then I have getRows() function which extracts the rows from the database and then returns it. Here is the code:

function __construct() {  
     mysql_connect("localhost","root","") or die(mysql_error());  
     mysql_select_db("TestProject") or die(mysql_error());  
}     

function getRows() {  
     $sql = "SELECT * FROM Record";  
     $this->arr2 = $this->queryString($sql);  
     //Declaring that $return is an array  
     $return = array();  
     foreach ($this->arr2 as $key=>$value) {  
           $return[$key] = $value;  
     }//foreach ends here  
     return $return;  
}     

function queryString($sql) {  
     $query =  mysql_query($sql);  
     $row = mysql_fetch_assoc($query);  
     return $row;  
}// function queryString ends here()  

Then on the other page, i use below code to fetch out everything from the objects returned and display it... But I dont understand whats going wrong!

$class = new fetch_assoc;  
$results = $class->getRows();  
//echo out everything  
foreach ($results as $result) {  
    foreach ($result as $key=>$value) {  
    echo "hello";    echo $key . ": " . $value;  
}//foreach ($result as $key=>$value) ends here  

Answer 1

$this->host = $db_config['host'];

Where I complete localhost at $this-> host or $db_config[' host ']

Answer 2

Your class fetches a single row from the table and stores the array on the object, which is then returned. However your code assumes that multiple rows are being returned.

Answer 3

Here is a quick example that might help you with your problem. Let's say I wanted to fetch an array of all my "Customer" data from my "customers" table, How would I successfully complete this task?

For this example I will be using two files:

• db.class.php: This class will hold all of the database functions.
• init.php: This file will require the database class to fetch all of the customer rows.

db.class.php

<?php

class DB {

  private $host;
  private $user;
  private $pw;
  private $db;

  public function __construct($db_config) {
    $this->host = $db_config['host']; 
    $this->user = $db_config['user'];
    $this->pw   = $db_config['pw'];
    $this->db   = $db_config['db'];
  }

  public function open() 
  {
    /* establish link */
    $link = new mysqli($this->host, $this->user, $this->pw, $this->db);

    if (!$link) {
      return false;
    }

    $link->autocommit(TRUE);

    return $link;
  }

  public function getRows($table) {

    /* establish database connection */
    $db = self::open();

    /* execute query */
    $result = $db->query("SELECT * FROM $table");

    /* fetch rows */
    while ($row = $result->fetch_array()) {
       $rows[] = $row;
    }

    return $rows;
  }

}

init.php

<?php

  require 'db.class.php';
  /* database config */
  $db_config = array(
                 'host' => '',
                 'user' => '',
                 'pw' => '',
                 'db' => ''
               );

  /* input table */
  $table = 'cust';

  $db = new DB($db_config);
  $rows = $db->getRows($table);

  foreach ($rows as $key => $value) {  
    echo 'Row: '.$key." : ".$value."<br />";  
  } 

?>

Answer 4

class db_mysql
{
    /**
    * Class instance
    *
    * @var object
    */
    private static $instance;

    /**
    * Connection to MySQL.
    *
    * @var string
    */
    protected $link;

    /**
    * Holds the most recent connection.
    *
    * @var string
    */
    protected $recent_link = null;

    /**
    * Holds the contents of the most recent SQL query.
    *
    * @var string
    */
    protected $sql = '';

    /**
    * Holds the number of queries executed.
    *
    * @var integer
    */
    public $query_count = 0;

    /**
    * The text of the most recent database error message.
    *
    * @var string
    */
    protected $error = '';

    /**
    * The error number of the most recent database error message.
    *
    * @var integer
    */
    protected $errno = '';

    /**
    * Do we currently have a lock in place?
    *
    * @var boolean
    */
    protected $is_locked = false;

    /**
    * Show errors? If set to true, the error message/sql is displayed.
    *
    * @var boolean
    */
    public $show_errors = false;

    /**
    * Database host
    *
    * @var string
    */
    protected static $db_host;

    /**
    * Database username
    *
    * @var string
    */
    protected static $db_user;

    /**
    * Database password
    *
    * @var string
    */
    protected static $db_pass;

    /**
    * Database name.
    *
    * @var string
    */
    protected static $db_name;

    /**
    * Constructor. Initializes a database connection and selects our database.
    *
    * private, cannot be accessed directly outside of this class
    *
    * @param  string   $db_host  Database host
    * @param  string   $db_user  Database username
    * @param  string   $db_pass  Database password
    * @param  string   $db_name  Database name
    * @return boolean            Connection resource, if database connection is established.
    */
    private function __construct()
    {
        self::set_params();

        $this->link = @mysql_connect(self::$db_host, self::$db_user, self::$db_pass);

        if (is_resource($this->link) AND @mysql_select_db(self::$db_name, $this->link))
        {
            $this->recent_link =& $this->link;
            return $this->link;
        }
        else
        {
            // If we couldn't connect or select the db...
            $this->raise_error('db_mysql::__construct() - Could not select and/or connect to database: ' . self::$db_name);
        }
    }

    /**
    * Creates an instance of the class.
    *
    * @param  void
    * @return object
    */
    public static function getInstance()
    {
        if (!self::$instance)
        {
            self::$instance = new self();
        }
        return self::$instance;
    }

    /**
    * Sets connection/database parameters.
    *
    * @param  void
    * @return void
    */
    protected static function set_params()
    {
        global $dbconfig;

        self::$db_host = $dbconfig['host'];
        self::$db_user = $dbconfig['user'];
        self::$db_pass = $dbconfig['pass'];
        self::$db_name = $dbconfig['name'];
    }

    /**
    * Executes a sql query. If optional $only_first is set to true, it will
    * return the first row of the result as an array.
    *
    * @param  string  Query to run
    * @param  bool    Return only the first row, as an array?
    * @return mixed
    */
    public function query($sql, $only_first = false)
    {
        $this->recent_link =& $this->link;
        $this->sql =& $sql;
        $result = @mysql_query($sql, $this->link);

        $this->query_count++;

        if ($only_first)
        {
            $return = $this->fetch_array($result);
            $this->free_result($result);
            return $return;
        }
        return $result;
    }

    /**
    * Fetches a row from a query result and returns the values from that row as an array.
    *
    * @param  string  The query result we are dealing with.
    * @return array
    */
    public function fetch_array($result)
    {
        return @mysql_fetch_assoc($result);
    }

    /**
    * Will fetch all records from the database, and will optionally return the
    * value of a single field from all records.
    *
    * @param  string  $sql    SQL Query string
    * @param  string  $field  Field/column
    * @return array           Will return array of all db records.
    */
    public function fetch_all($sql, $field = '')
    {
        $return = array();

        if (($result = $this->query($sql)))
        {
            while ($row = $this->fetch_array($result))
            {
                $return[] = ($field) ? $row[$field] : $row;
            }
            $this->free_result($result);
        }
        return $return;
    }

    /**
    * Returns the number of rows in a result set.
    *
    * @param  string  The query result we are dealing with.
    * @return integer
    */
    public function num_rows($result)
    {
        return @mysql_num_rows($result);
    }

    /**
    * Retuns the number of rows affected by the most recent query
    *
    * @return integer
    */
    public function affected_rows()
    {
        return @mysql_affected_rows($this->recent_link);
    }

    /**
    * Returns the number of queries executed.
    *
    * @param  none
    * @return integer
    */
    public function num_queries()
    {
        return $this->query_count;
    }

    /**
    * Lock database tables
    *
    * @param   array  Array of table => lock type
    * @return  void
    */
    public function lock($tables)
    {
        if (is_array($tables) AND count($tables))
        {
            $sql = '';

            foreach ($tables AS $name => $type)
            {
                $sql .= (!empty($sql) ? ', ' : '') . "$name $type";
            }

            $this->query("LOCK TABLES $sql");
            $this->is_locked = true;
        }
    }

    /**
    * Unlock tables
    */
    public function unlock()
    {
        if ($this->is_locked)
        {
            $this->query("UNLOCK TABLES");
            $this->is_locked = false; 
        }
    }

    /**
    * Returns the ID of the most recently inserted item in an auto_increment field
    *
    * @return  integer
    */
    public function insert_id()
    {
        return @mysql_insert_id($this->link);
    }

    /**
    * Escapes a value to make it safe for using in queries.
    *
    * @param  string  Value to be escaped
    * @param  bool    Do we need to escape this string for a LIKE statement?
    * @return string
    */
    public function prepare($value, $do_like = false)
    {
        $value = stripslashes($value);

        if ($do_like)
        {
            $value = str_replace(array('%', '_'), array('\%', '\_'), $value);
        }
        return mysql_real_escape_string($value, $this->link);
    }

    /**
    * Frees memory associated with a query result.
    *
    * @param  string   The query result we are dealing with.
    * @return boolean
    */
    public function free_result($result)
    {
        return @mysql_free_result($result);
    }

    /**
    * Turns database error reporting on
    */
    public function show_errors()
    {
        $this->show_errors = true;
    }

    /**
    * Turns database error reporting off
    */
    public function hide_errors()
    {
        $this->show_errors = false;
    }

    /**
    * Closes our connection to MySQL.
    *
    * @param  none
    * @return boolean
    */
    public function close()
    {
        $this->sql = '';
        return @mysql_close($this->link);
    }

    /**
    * Returns the MySQL error message.
    *
    * @param  none
    * @return string
    */
    public function error()
    {
        $this->error = (is_null($this->recent_link)) ? '' : mysql_error($this->recent_link);
        return $this->error;
    }

    /**
    * Returns the MySQL error number.
    *
    * @param  none
    * @return string
    */
    function errno()
    {
        $this->errno = (is_null($this->recent_link)) ? 0 : mysql_errno($this->recent_link);
        return $this->errno;
    }

    /**
    * Gets the url/path of where we are when a MySQL error occurs.
    *
    * @access private
    * @param  none
    * @return string
    */
    protected function get_error_path()
    {
        if ($_SERVER['REQUEST_URI'])
        {
            $errorpath = $_SERVER['REQUEST_URI'];
        }
        else
        {
            if ($_SERVER['PATH_INFO'])
            {
                $errorpath = $_SERVER['PATH_INFO'];
            }
            else
            {
                $errorpath = $_SERVER['PHP_SELF'];
            }

            if ($_SERVER['QUERY_STRING'])
            {
                $errorpath .= '?' . $_SERVER['QUERY_STRING'];
            }
        }

        if (($pos = strpos($errorpath, '?')) !== false)
        {
            $errorpath = urldecode(substr($errorpath, 0, $pos)) . substr($errorpath, $pos);
        }
        else
        {
            $errorpath = urldecode($errorpath);
        }
        return $_SERVER['HTTP_HOST'] . $errorpath;
    }

    /**
    * If there is a database error, the script will be stopped and an error message displayed.
    *
    * @param  string  The error message. If empty, one will be built with $this->sql.
    * @return string
    */
    public function raise_error($error_message = '')
    {
        if ($this->recent_link)
        {
            $this->error = $this->error($this->recent_link);
            $this->errno = $this->errno($this->recent_link);
        }

        if ($error_message == '')
        {
            $this->sql = "Error in SQL query:\n\n" . rtrim($this->sql) . ';';
            $error_message =& $this->sql;
        }
        else
        {
            $error_message = $error_message . ($this->sql != '' ? "\n\nSQL:" . rtrim($this->sql) . ';' : '');
        }

        $message = htmlspecialchars("$error_message\n\nMySQL Error: {$this->error}\nError #: {$this->errno}\nFilename: " . $this->get_error_path());
        $message = '<code>' . nl2br($message) . '</code>';

        if (!$this->show_errors)
        {
            $message = "<!--\n\n$message\n\n-->";
        }
        die("There seems to have been a slight problem with our database, please try again later.<br /><br />\n$message");
    }
}

that was a secure class i used to write long time ago its easy use for sure here is an example

$dbconfig = array(
    'host' => SERVER,
    'user' => USER,
    'pass' => PASSWORD,
    'name' => DBNAME
);
$db = db_mysql::getInstance();
$getmaxcategories = $db->query("SELECT * FROM categories");
if($db->num_rows($getmaxcategories) != "0")
 {
while($row = $db->fetch_array($getmaxcategories))
      {
               //do something
      }
  }

you can use foreach for loop or whatever