Single Responsibility Principle?

[terrydoang]

I know that each class should follow SRP.
But, does this code below violate SRP ?

<?php
namespace LibraryDatabase;
 
class PdoAdapter implements DatabaseAdapterInterface
{
    protected $config = array();
    protected $connection;
    protected $statement;
    protected $fetchMode = PDO::FETCH_ASSOC;   
     
    public function __construct($dsn, $username = null,
        $password = null, array $driverOptions = array()) {
        $this->config = compact("dsn", "username", "password", 
            "driverOptions");
    }
 
    public function getStatement() {
        if ($this->statement === null) {
            throw new PDOException(
              "There is no PDOStatement object for use.");
        } 
        return $this->statement;
    }
     
    public function connect() {
        // if there is a PDO object already, return early
        if ($this->connection) {
            return;
        }
  
        try {
            $this->connection = new PDO(
                $this->config["dsn"],
                $this->config["username"],
                $this->config["password"],
                $this->config["driverOptions"]);
            $this->connection->setAttribute(PDO::ATTR_ERRMODE,
                PDO::ERRMODE_EXCEPTION);
            $this->connection->setAttribute(
                PDO::ATTR_EMULATE_PREPARES, false); 
        }
        catch (PDOException $e) {
            throw new RunTimeException($e->getMessage());
        }
    }
     
    public function disconnect() {
        $this->connection = null;
    }
     
    public function prepare($sql, array $options = array() {
        $this->connect();
        try {
            $this->statement = $this->connection->prepare($sql, 
                $options);
            return $this;
        }
        catch (PDOException $e) {
            throw new RunTimeException($e->getMessage());
        }
    }
     
    public function execute(array $parameters = array()) {
        try {
            $this->getStatement()->execute($parameters);
            return $this;
        }
        catch (PDOException $e) {
            throw new RunTimeException($e->getMessage());
        }
    }
     
    public function countAffectedRows() {
        try {
            return $this->getStatement()->rowCount();
        }
        catch (PDOException $e) {
            throw new RunTimeException($e->getMessage());
        }
    }
 
    public function getLastInsertId($name = null) {
        $this->connect();
        return $this->connection->lastInsertId($name);
    }
     
    public function fetch($fetchStyle = null,
        $cursorOrientation = null, $cursorOffset = null) {
        if ($fetchStyle === null) {
            $fetchStyle = $this->fetchMode;
        }
  
        try {
            return $this->getStatement()->fetch($fetchStyle, 
                $cursorOrientation, $cursorOffset);
        }
        catch (PDOException $e) {
            throw new RunTimeException($e->getMessage());
        }
    }
      
    public function fetchAll($fetchStyle = null, $column = 0) {
        if ($fetchStyle === null) {
            $fetchStyle = $this->fetchMode;
        }
  
        try {
            return $fetchStyle === PDO::FETCH_COLUMN
               ? $this->getStatement()->fetchAll($fetchStyle, $column)
               : $this->getStatement()->fetchAll($fetchStyle);
        }
        catch (PDOException $e) {
            throw new RunTimeException($e->getMessage());
        }
    }
     
    public function select($table, array $bind = array(), 
        $boolOperator = "AND") {
        if ($bind) {
            $where = array();
            foreach ($bind as $col => $value) {
                unset($bind[$col]);
                $bind[":" . $col] = $value;
                $where[] = $col . " = :" . $col;
            }
        }
  
        $sql = "SELECT * FROM " . $table
            . (($bind) ? " WHERE "
            . implode(" " . $boolOperator . " ", $where) : " ");
        $this->prepare($sql)
            ->execute($bind);
        return $this;
    }
     
    public function insert($table, array $bind) {
        $cols = implode(", ", array_keys($bind));
        $values = implode(", :", array_keys($bind));
        foreach ($bind as $col => $value) {
            unset($bind[$col]);
            $bind[":" . $col] = $value;
        }
  
        $sql = "INSERT INTO " . $table
            . " (" . $cols . ")  VALUES (:" . $values . ")";
        return (int) $this->prepare($sql)
            ->execute($bind)
            ->getLastInsertId();
    }
     
    public function update($table, array $bind, $where = "") {
        $set = array();
        foreach ($bind as $col => $value) {
            unset($bind[$col]);
            $bind[":" . $col] = $value;
            $set[] = $col . " = :" . $col;
        }
  
        $sql = "UPDATE " . $table . " SET " . implode(", ", $set)
            . (($where) ? " WHERE " . $where : " ");
        return $this->prepare($sql)
            ->execute($bind)
            ->countAffectedRows();
    }
     
    public function delete($table, $where = "") {
        $sql = "DELETE FROM " . $table . (($where) ? " WHERE " . $where : " ");
        return $this->prepare($sql)
            ->execute()
            ->countAffectedRows();
    }
}

I get the code in http://www.sitepoint.com/integrating-the-data-mappers/

Does it violate SRP ?
What I think is that the class has 2 responsibility, because it also responsibles for the statement, while original PHP separates PDO and PDOStatement.

[TomB]

It also contains specific SQL statements, with SRP you should have the database connection stuff and the database operations in different places.

I also question the usefulness of this class. What does this achieve that PDO does not? Pdo itself is a database adapter class.

[terrydoang]

Yes, but PDO doesn’t have an interface…

[Michael_Morris]

It doesn’t need one.