PHP性能：“全局”关键字在功能上比“包含”更好吗？

Question

Let's pretend I have a database.php file which contains a persistent access to the database.

<?php
$database = new PDO('mysql:host=xxx', "xxx", "xxx", array(
    PDO::ATTR_PERSISTENT => true
));
?>

Every time I want to query the database within a controller, what should I do?

1/ Use the global keyword to get my global $database variable

<?php

include '../app/config/Database.php';

function getLastOfTheWeek()
{
    global $database;
    $database->query('SELECT * FROM `xxx`');
    ...
}
?>

2/ Include database.php within the function

<?php

function getLastOfTheWeek()
{
    include '../app/config/Database.php';
    $database->query('SELECT * FROM `xxx`');
    ...
}
?>

3/ Give this man some doc, he needs it

Or both are evil anyway, and I should use another method.

Answer 1

1. Global state is bad.
2. Repeatedly creating DB connections is bad.

Good:

$dbh = new PDO (...);

function doSomething($dbh) {
  $dbh->query(...);
}

OK:

class Something {
  protected $dbh;

  public function __construct($db_config) {
    $this->dbh = new PDO($db_config); // still bad
  }

  public function doSomething() {
    $this->dbh->query();
  }
}

God Tier:

class Something {
  protected $dbh;

  public function __construct(PDO $dbh) {
    $this->dbh = $dbh;
  }

  public function doSomething() {
    $this->dbh->query();
  }
}

$dbh = new PDO(...);
$s = new Something($dbh);
$s->doSomething;

See: http://www.phptherightway.com/#dependency_injection