Air-Quality-Web/logic/Database.php

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<?php
namespace AirQuality;
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use \SBRL\TomlConfig;
use Psr\Container\ContainerInterface;
/**
* Holds the main database connection.
*/
class Database
{
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/** @var TomlConfig */
private $settings;
/** @var \SBRL\PerformanceCounter */
private $perfcounter;
/**
* Whether the database connection should be read only or not.
* Defaults to true, as we don't need to write _anything_ to the database.
* @var bool
*/
private const read_only = true;
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/**
* The internal PDO connection to the database.
* @var \PDO
*/
private $connection;
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/**
* The PDO connection options.
* @var array
*/
private $pdo_options = [
// https://devdocs.io/php/pdo.setattribute
\PDO::ATTR_ERRMODE => \PDO::ERRMODE_EXCEPTION,
\PDO::ATTR_DEFAULT_FETCH_MODE => \PDO::FETCH_ASSOC,
\PDO::ATTR_EMULATE_PREPARES => false,
\PDO::ATTR_AUTOCOMMIT => false
];
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/**
* Initialises a new Database class instance that manages a single
* connection to a database.
* @param TomlConfig $in_settings The settings object to use to connect to the database
* @param \SBRL\PerformanceCounter $in_perfcounter The performance counter for debugging purposes.
*/
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function __construct(TomlConfig $in_settings, \SBRL\PerformanceCounter $in_perfcounter) {
$this->settings = $in_settings;
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$this->perfcounter = $in_perfcounter;
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$this->connect(); // Connect automagically
}
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/**
* Initailises the connection to the database according to the currently loaded settings.
* @return void
*/
public function connect() {
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$this->perfcounter->start("dbconnect");
$this->connection = new \PDO(
$this->get_connection_string(),
$this->settings->get("database.username"),
$this->settings->get("database.password"),
$this->pdo_options
);
// Make this connection read-only
if(self::read_only)
$this->connection->query("SET SESSION TRANSACTION READ ONLY;");
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$this->perfcounter->end("dbconnect");
}
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/**
* Makes a query against the database.
* @param string $sql The (potentially parametised) query to make.
* @param array $variables Optional. The variables to substitute into the SQL query.
* @return \PDOStatement The result of the query, as a PDOStatement.
*/
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public function query($sql, $variables = []) {
// Replace tabs with spaces for debugging purposes
$sql = str_replace("\t", " ", $sql);
if($this->settings->get("env.mode") == "development") {
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error_log("[Database/SQL:Variables]" . var_export($variables, true));
error_log("[Database/SQL:Exec] $sql");
}
// FUTURE: Optionally cache prepared statements?
$statement = $this->connection->prepare($sql);
$statement->execute($variables);
if($this->settings->get("env.mode") == "development") {
$warnings = $this->connection->query("SHOW WARNINGS;")->fetchAll();
error_log("Warnings: " . var_export($warnings, true));
}
return $statement; // fetchColumn(), fetchAll(), etc. are defined on the statement, not the return value of execute()
}
/**
* Returns the connection string to use to connect to the database.
* This is calculated from the values specified in the settings file.
* @return string The connection string.
*/
private function get_connection_string() {
return "{$this->settings->get("database.type")}:host={$this->settings->get("database.host")};dbname={$this->settings->get("database.name")};charset=utf8mb4";
}
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}