查询在自定义PDO数据库类中运行两次

I'm currently attempting to create my own custom database class that will allow me to do basic things such as insert, update, and select from my database. I have the code working for my insert function but it's inserting twice and I'm not sure why. It's been a while since I've messed with the singleton pattern and am having quite a few issues today. Any help would be great. Thanks

The issue method in question here is the insert() method. It uses the db() method to get it's instance of the database connection.

Database.php

class Database {
    // Class Properties
    private static $_instance;
    public $pdo;

    /**
     * Returns a database connection
     * @return resource Database Connection
     */
    private static function db() {
        // Return Database Connection
        return Database::getInstance()->getConnection();
    }

    private function getConnectionProperties($property) {
        return $GLOBALS['config']['database'][$property];
    }

    /**
     * Singleton for database connection
     * @return class Returns one instance of the Database class
     */
    public static function getInstance() {
        if(!self::$_instance) {
            self::$_instance = new self();
        }
        return self::$_instance;
    }

    /**
     * Connects to database
     * @return mysql PDO connection to mysql databse
     */
    public function getConnection() {
        try {
            //Attempt to connect
            $this->pdo = new PDO('mysql:host=' . $this->getConnectionProperties('host') . ';dbname=' . $this->getConnectionProperties('database') , $this->getConnectionProperties('username'), $this->getConnectionProperties('password'));

            //Return connection
            return $this->pdo;
        } catch (PDOException $e) {
            throw new PDOException($e);
        }
    }

    public static function insert($table, $params) {
        // Define initial query
        $query = "INSERT INTO `{$table}` (";

        // Format rows to insert
        foreach(array_keys($params) as $field) {
            $fields .= $field . ",";
            $bindParams .= ":" . $field . ",";
        }

        // Add rows and bind params to query
        $query .= rtrim($fields, ',') . ") VALUES(" . rtrim($bindParams, ',') . ")";

        // Prepare Query
        $preparedQuery = self::db()->prepare($query);

        foreach($params as $key => $value) {
            $queryParams[':' . $key] = $value;
        }

        //Execute Query
        if($preparedQuery->execute($queryParams)) {

        }
   }
}

Calling Database::Insert

Database::insert("test_table", [
    'username' => "Joe_Scotto",
    'name' => "Joe"
]);

This code does work, the only issue is that it runs twice. I think this has something to do with the class getting instantiated twice but am not sure.

I had to rewrite a large portion of the class to get it working. This is the code that worked:

// Class Properties
private static $_instance = null;
private $_pdo;

/**
 * Grabs connection variables
 * @param  string $property Variable to grab from the config file
 * @return string           Returns a config value
 */
private function getConnectionProperties($property) {
    return $GLOBALS['config']['database'][$property];
}

/**
 * Returns pdo connection
 * @return resource PDO Object
 */
public function getConnection() {
    return $this->_pdo;
}

/**
 * Connects to database
 * @return mysql PDO connection to mysql databse
 */
public function __construct() {
    try {
        //Attempt to create connection
        $this->_pdo = new PDO('mysql:host=' . $this->getConnectionProperties('host') . ';dbname=' . $this->getConnectionProperties('database') , $this->getConnectionProperties('username'), $this->getConnectionProperties('password'));
    } catch (PDOException $e) {
        throw new PDOException($e);
    }
}

/**
 * Singleton for database connection
 * @return class Returns one instance of the Database class
 */
public static function getInstance() {
    if(!self::$_instance) {
        self::$_instance = new self();
    }
    return self::$_instance;
}

/**
 * Inserts into the database
 * @param  string $table  The table to insert into
 * @param  array  $params Key and value pairs for use within the query
 * @return bool           True on success, false on failure
 */
public static function insert($table, $params) {
    // Define initial query
    $query = "INSERT INTO `{$table}` (";

    // Format rows to insert
    foreach($params as $key => $value) {
        $fields .= $key . ",";
        $bindParams .= ":" . $key . ",";
        $queryParams[':' . $key] = $value;
    }

    // Add rows and bind params to query
    $query .= rtrim($fields, ',') . ") VALUES(" . rtrim($bindParams, ',') . ")";

    // Prepare Query
    $preparedQuery = self::getInstance()->getConnection()->prepare($query);

    // Attempt to execute Query
    if(!$preparedQuery->execute($queryParams)) {
        return false;
    }

    // If everything passes, return true
    return true;
}