函数：将指针传递给$ con

Question

I'm displaying a relatively "heavy" PHP page. I have several functions that each use a connection to the DB to grab some rows. I've noticed that making a new $con in each function slows things down a lot, so naturally I would like to use the same $con for each function on the page. I tried this:

$con = mysqli_connect("localhost","root","root", "mydb");

function fA($a, $b, &$con = $con)
{}

function fB($a, &$con = $con)
{}

You can see I'm trying to pass a pointer to $con for each function, but I get a syntax error, unexpected $con for each one. (I could pass $con to the functions whenever I call them but doing it this way I don't have to go back and change every function call, and it looks neater)

Answer 1

You can use:

global $con;

At the beginning of each function's body like so:

function fA($a, $b) {
    global $con
    // ...etc...
}

But this is generally viewed as a bad practice.

A better approach would be to use dependency injection so that your logic would not be dependent on the kind of storage device given to it. Something along these lines:

class LogicExecutor {
    private $con;

    public __construct($con) {
        $this->con = $con;
    }

    public function doTaskOne($a, $b) {
        // you can use $this->con in this scope
    }
}

$con = mysqli_connect('localhost', 'root', 'root', 'mydb');
$le = new LogicExecutor($con);

$le->doTaskOne('a','b');

But even that would couple your code to mysqli very tightly. Have you considered an ORM?