php - 如何通过id查询数据库中的所有条目？

Question

我正在关注 Udemy 上有关构建登录表单的教程。一切顺利。

现在我正在尝试重用代码。我遇到的问题是当我试图查询数据库中的所有条目以获取网站总数时。你能给点建议吗？

这是我的计数函数(这是我在获取数据库条目总数以进行分页时遇到问题的地方):

function get_all_websites(){

        $all = array();

        $db = DB::getInstance();
        $all = $db->query("SELECT * FROM website");

        if(!$all->count()){
            echo 'No Websites available. Please check back later.';
        } else {
            foreach($all->results() as $all){
                $all->id = $all;
            }
        }

        return $all;

    }

    function get_websites_count(){

        return count(get_all_websites());

    }

如果我使用它，我会列出所有 ID。

function get_all_websites(){

    $all = array();

    $db = DB::getInstance();
    $all = $db->query("SELECT * FROM website");

    if(!$all->count()){
        echo 'No Websites available. Please check back later.';
    } else {
        foreach($all->results() as $all){
            echo $all->id;
        }
    }

}

数据库类。

class DB{
        private static $_instance = null;
        private $_pdo,
                $_query,
                $_error = false,
                $_results,
                $_count = 0;


        private function __construct(){

            try {
                $this->_pdo = new PDO('mysql:host=' .
                        Config::get('mysql/host') . ';dbname=' .
                        Config::get('mysql/db'),
                        Config::get('mysql/username'),
                        Config::get('mysql/password'));

            } catch(PDOException $e){
                die($e -> getMessage());
            }
        }

        public static function getInstance(){
            if(!isset(self::$_instance)) {
                self::$_instance = new DB();
            }
            return self::$_instance;
        }

        public function query($sql, $params = array()){

            $this->_error = false;

            // Check if query has been prepared properly

            if($this->_query = $this->_pdo->prepare($sql)){

                $x = 1;
                if(count($params)){
                    foreach($params as $param){
                        $this->_query->bindValue($x, $param);
                        $x++;
                    }
                }

            // If the query has been prepared successfuly, store the result
                if($this->_query->execute()){
                    $this->_results = $this->_query->fetchAll(PDO::FETCH_OBJ);
                    $this->_count = $this->_query->rowCount();
                } else {
                    $this->_error = true;
                }
            }

            return $this;
        }

        public function action($action, $table, $where = array()){
            if(count($where) === 3){
                $operators = array('=', '>', '<', '>=', '<=');

                $field      = $where[0];
                $operator   = $where[1];
                $value      = $where[2];

                if(in_array($operator, $operators)){
                    $sql = "{$action} FROM {$table} WHERE {$field} {$operator} ?";

                    if(!$this->query($sql, array($value))->error()){
                        return $this;
                    }
                }
            }

            return false;
        }

        // QUERYING DATA FROM DATABASE
        public function get($table, $where){
            return $this->action('SELECT *', $table, $where);
        }

        // DELETING DATA FROM DATABASE
        public function delete($table, $where){
            return $this->action('DELETE', $table, $where);
        }

        // INSERTING DATA INTO DATABASE
        public function insert($table, $fields = array()){
                $keys = array_keys($fields);
                $values = '';
                $x = 1;

                foreach($fields as $field){
                    $values .= "?";

                    if($x < count($fields)){
                        $values .= ', ';
                    }
                    $x++;
                }

                $sql = "INSERT INTO {$table} (`" . implode('`, `', $keys) . "`) VALUES({$values})";

                if(!$this->query($sql, $fields)->error()){
                    return true;
                }

            return false;
        }

        public function results(){
            return $this->_results;
        }

        public function update($table, $id, $fields){
            $set = '';
            $x = 1;

            foreach($fields as $name => $value){
                $set .= "{$name} = ?";

                if($x < count($fields)){
                    $set .= ', ';
                }
                $x++;
            }


            $sql = "UPDATE {$table} SET {$set} WHERE id = {$id}";

            if(!$this->query($sql, $fields)->error()){
                return true;
            }

            return false;
        }

        public function first(){
            return $this->results()[0];
        }

        public function error(){
            return $this->_error;
        }

        public function count(){
            return $this->_count;
        }

    }

Answer 1

这部分好像不太对:

    } else {
        foreach($all->results() as $all){
            $all->id = $all;
        }
    }
    return $all;

但我不太确定你想要什么。

我们可以将每个 id 附加到一个名为 $allWebsiteIds 的数组中:

    } else {
        foreach($all->results() as $all){
            $allWebsiteIds[] = $all->id;
        }
    }
    return $allWebsiteIds;

这可能会给你你想要的。