php实现的pdo公共类定义与用法示例

<?php
class db extends \pdo {
  private static $_instance = null;
  protected $dbname = '';
  protected $dsn;
  protected $dbh;
  public function __construct($dbhost, $dbuser, $dbpasswd, $dbname, $dbcharset='utf8') {
    try {
      $this->dsn = 'mysql:host=' . $dbhost . ';dbname=' . $dbname;
      $this->dbh = new \pdo($this->dsn, $dbuser, $dbpasswd);
      $this->dbh->setattribute(\pdo::attr_emulate_prepares, false);
      $this->dbh->setattribute(\pdo::attr_errmode, \pdo::errmode_exception);
      $this->dbh->exec('set character_set_connection='.$dbcharset.';set character_set_client='.$dbcharset.';set character_set_results='.$dbcharset);
    } catch (exception $e) {
      $this->outputerror($e->getmessage()); 
    }
  }
  public static function getinstance($dbhost, $dbuser, $dbpasswd, $dbname, $dbcharset='utf8') {
    if (self::$_instance === null) {
      self::$_instance = new self($dbhost, $dbuser, $dbpasswd, $dbname, $dbcharset);
    }
    return self::$_instance;
  }
  public function fetchall($sql, $params = array()) {
    try {
      $stm = $this->dbh->prepare($sql);
      if ($stm && $stm->execute($params)) {
        return $stm->fetchall(\pdo::fetch_assoc);
      }
    } catch (exception $e) {
      $this->outputerror($e->getmessage());
    }
  }
  public function fetchone($sql, $params = array()) {
    try {
      $result = false;
      $stm = $this->dbh->prepare($sql);
      if ($stm && $stm->execute($params)) {
        $result = $stm->fetch(\pdo::fetch_assoc);
      }
      return $result;
    } catch (exception $e) {
      $this->outputerror($e->getmessage());
    }
  }
  public function fetchcolumn($sql, $params = array()) {
    $result = '';
    try {
      $stm = $this->dbh->prepare($sql);
      if ($stm && $stm->execute($params)) {
        $result = $stm->fetchcolumn();
      }
      return $result;
    } catch (exception $e) {
      $this->outputerror($e->getmessage());
    }
  }
  public function insert($table, $params = array(), $returnlastid = true) {
    $_implode_field = '';
    $fields = array_keys($params);
    $_implode_field = implode(',', $fields);
    $_implode_value = '';
    foreach ($fields as $value) {
      $_implode_value .= ':'. $value.',';
    }
    $_implode_value = trim($_implode_value, ',');
    $sql = 'insert into ' . $table . '(' . $_implode_field . ') values ('.$_implode_value.')';
    try {
      $stm = $this->dbh->prepare($sql);
      $result = $stm->execute($params);
      if ( $returnlastid ) {
        $result = $this->dbh->lastinsertid();
      }
      return $result;
    } catch (exception $e) {
      $this->outputerror($e->getmessage());
    }
  }
  public function update($table, $params = array(), $where = null) {
    $_implode_field = '';
    $_implode_field_arr = array();
    if ( empty($where) ) {
      return false;
    }
    $fields = array_keys($params);
    foreach ($fields as $key) {
      $_implode_field_arr[] = $key . '=' . ':'.$key;
    }
    $_implode_field = implode(',', $_implode_field_arr);
    $sql = 'update ' . $table . ' set ' . $_implode_field . ' where ' . $where;
    try {
      $stm = $this->dbh->prepare($sql);
      $result = $stm->execute($params);
      return $result;
    } catch (exception $e) {
      $this->outputerror($e->getmessage());
    }
  }
  public function delete($sql, $params = array()) {
    try {
      $stm = $this->dbh->prepare($sql);
      $result = $stm->execute($params);
      return $result;
    } catch (exception $e) {
      $this->outputerror($e->getmessage());
    }
  }
  public function exec($sql, $params = array()) {
    try {
      $stm = $this->dbh->prepare($sql);
      $result = $stm->execute($params);
      return $result;
    } catch (exception $e) {
      $this->outputerror($e->getmessage());
    }
  }
  private function outputerror($strerrmsg) {
    throw new exception("mysql error: " . $strerrmsg);
  }
  public function __destruct() {
    $this->dbh = null;
  }
}

<?php
require_once './db.class.php';
$pdo = db::getinstance('127.0.0.1', 'root', '111111', 'php_cms');
$sql = "select id, title1 from cms_wz where id = :id limit 1";
$parame = array('id' => 12,);
$res = $pdo->fetchone($sql, $parame);
var_dump($res);
$sql = 'select * from cms_link';
$result = $db->fetchall($sql);
print_r($result);
//查询记录数量
$sql = 'select count(*) from cms_link';
$count = $db->fetchcolumn($sql);
echo $count;
$data = array(
  'siteid' => 1,
  'linktype' => 1,
  'name' => 'google',
  'url' => 'http://www.google.com',
  'listorder' => 0,
  'elite' => 0,
  'passed' => 1,
  'addtime' => time()
  );
$lastinsertid = $db->insert('cms_link', $data);
echo $lastinsertid;
//用 try
 try {
     $result = $pdo->insert('news', $essay);
   } catch (exception $e) {
     error_log($e->getmessage());
     error_log($e->getmessage() . ' in ' . __file__ . ' on line ' . __line__);
     savelog('url文章 : ' . $essay['link'] . '  数据插入失败<br>');
     continue;
   }
$data = array(
  'siteid' => 1,
  'linktype' => 1,
  'name' => 'google',
  'url' => 'http://www.google.com',
  'listorder' => 0,
  'elite' => 0,
  'passed' => 1,
  'addtime' => time()
  );
$db->insert('cms_link', $data);
$sql = 'delete from cms_link where linkid=4';
$result = $db->delete($sql);
var_dump($result);