How do I pass a database connection into a method PHP - php

Question

I have a class in PHP and one of the methods needs to access a database.How do I correctly pass a database connection variable to a method? Does it get passed as a parameter through the constructor or method? Or is it something completely different?

Answer 1

Check the following updated answer. Tested and working.
<?php
class SomeClass
{
function setDb($servername, $username, $password, $database)
{
// Create the database connection and use this connection in your methods as $this->conn
$this->conn = new mysqli($servername, $username, $password, $database);
if ($this->conn->connect_error) {
die("Connection failed: " . $this->conn->connect_error);
}
echo "New successful connection to myDb \n";
}
public function createTable()
{
// sql to create table
$sql = "CREATE TABLE MyGuests (
id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
firstname VARCHAR(30) NOT NULL,
lastname VARCHAR(30) NOT NULL,
email VARCHAR(50),
reg_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
)";
if ($this->conn->query($sql) === TRUE) {
echo "New table created successfully \n";
} else {
echo "Error: " . $sql . "<br>" . $this->conn->error;
}
}
public function normalInsertDb()
{
// sql to insert record using normal query
$sql = "INSERT INTO MyGuests (firstname, lastname, email)
VALUES ('John', 'Doe', 'john#example.com')";
if ($this->conn->query($sql) === TRUE) {
echo "New record inserted successfully using normal sql statement \n";
} else {
echo "Error: " . $sql . "<br>" . $this->conn->error;
}
}
public function preparedInsertDb()
{
// prepare and bind
$stmt = $this->conn->prepare("INSERT INTO MyGuests (firstname, lastname, email) VALUES (?, ?, ?)");
$stmt->bind_param("sss", $firstname, $lastname, $email);
// set parameters and execute
$firstname = "John";
$lastname = "Doe";
$email = "john#example.com";
$stmt->execute();
$firstname = "Mary";
$lastname = "Moe";
$email = "mary#example.com";
$stmt->execute();
$firstname = "Julie";
$lastname = "Dooley";
$email = "julie#example.com";
$stmt->execute();
echo "New records inserted successfully using PREPARED STATEMENTS \n";
$stmt->close();
$this->conn->close();
}
}
$obj = new SomeClass();
$obj->setDb('localhost', 'homestead', 'secret', 'myDb'); //we assume the database myDb exists
$obj->createTable();
$obj->normalInsertDb();
$obj->preparedInsertDb();
My Result:

Answer 2

If the database connection is used only by one method of your object, there is nothing wrong about passing it as an argument to this method.
However, mostly this is not the case. So you would be better off, when you establish the db connection at an earlier stage (on top of your script) and then pass it as a constructor argument to all objects that will need it. Then, various objects can use the same connection for various methods and internal, private methods, too.
If you want to optimize further, wrap the connection into a dedicated class and use dependency injection to get it into the consumer objects.