PDO connection and prepared statements - php

Question

Problem:
I have read quite a number of articles and two books about PDO but I do not seem to find the answer to my question. The question is whether there is a way to include the database connection to PDO as a require_once() and still be able to use prepared statements without a try/catch block?
I currently have a file called settings.php containing the following code.
Code (settings.php):
<?php
// Declaration of database connection information
$settings = [
'host' => '127.0.0.1',
'name' => 'c9',
'port' => '3306',
'charset' => 'utf8',
'username' => 'admin',
'password' => 'root'
];
?>
I put this file outside the document root and include it with require_once() to the actual database connection file.
Code (db.php):
<?php
// Includes database connection information
require_once('../settings.php');
// Connects to a MySQL database
try {
$dbh = new PDO(
sprintf(
'mysql:host=%s;dbname=%s;port=%s;charset=%s',
$settings['host'],
$settings['name'],
$settings['port'],
$settings['charset']
),
$settings['username'],
$settings['password']
);
// Prevents PDO to use emulated prepares and activates error
// mode PDO::ERRMODE_EXCEPTION
$dbh->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
// Catches errors raised by PDO
catch (PDOException $e) {
// Prints out errors to text file
file_put_contents('errors.txt', $e->getMessage(), FILE_APPEND);
// Shows generic error message to user
header('Location: 404.php');
exit;
}
?>
Questions:
Since I have the file db.php is it possible to include this in other files for prepared statements? Can prepared statements also be in try/catch block despite that the connection is in one? Appreciate any comments of how to include SELECT / INSERT / UPDATE / DELETE to the aforementioned code.

Answer 1

You've got a lot of unnecessary code there.
1) The try/catch is redundant because PHP will log your errors to the error log by default anyway. Besides, any thing that's going to be helpful will come from the execute() call.
2) Yes you can certainly include your database credentials wherever you want, but keep in mind, require_once() is expensive so make it count. You might consider including the whole block of code on all your other pages instead of just including the credentials and then rewriting the other code.
3) And example of a select statement from your above code would be:
$stmt = $dbh->prepare("SELECT * FROM `table` WHERE `id` = :id");
$stmt->execute(array(":id"=>$id));
$results = $stmt->fetch(PDO::FETCH_ASSOC);

Answer 2

Your question seems to be quite unclear, consists of highly irrelevant parts. Say, there is no connection between prepared statements and a try-catch block, both has nothing to do with include. And there is no particular guide on including SELECT / INSERT / UPDATE / DELETE queries in the code - you just run them wherever you wish.
I can make only some notes, hoping it will clear some of your confusions.
First of all, read my article on PDO. It is still incomplete but it may help you to sort things out.
Now to your questions.
whether there is a way to include the database connection to PDO as a require_once() and still be able to use prepared statements without a try/catch block?
Yes. In most cases you don't need a try catch block at all. However, every time you really need it, you can use a try catch block with no problem.
is it possible to include this in other files for prepared statements?
Yes. That's what include operator is for.
Can prepared statements also be in try/catch block despite that the connection is in one?
Yes. You can have as many such blocks in your code, as you need. However, in most cases you don't need them at all.
how to include SELECT / INSERT / UPDATE / DELETE to the aforementioned code.
There is no point in including these queries there. Just write them after the line where you included your db.php