Is die function accept only strings? - php

Question

this code works:
if (isset($db->error)) {
echo $db->error;
}
This code in not working:
if (isset($db->error)) {
die($db->error);
}
This is my DB class:
class Db {
private $db,
$error;
public function __construct() {
return $this->db = new mysqli(DB_SERVER, DB_USER, DB_PASS, D_NAME);
if ($this->db->connect_error) {
$this->error = $this->db->connect_error;
}
}
}
"D_NAME" is wrong so an error appears but I didn't kill the page, content still appear after the error. Why? Thanks!

Answer 1

The if block in the constructor is never executed, because you are returning $this->db:
public function __construct() {
return $this->db = new mysqli(DB_SERVER, DB_USER, DB_PASS, D_NAME);
// the lines after return will never be executed!
}
This is the first reason why the $db->error is unset.
The second reason is that the $error member is private, which means that you are not allowed to access this property directly. So you should make it accessible in one of the following ways (at least):
make it public;
implement the __get and __isset magic methods;
implement a getter method.
Using public $error
class Db {
private $db;
public $error;
public function __construct() {
$this->db = new mysqli('localhost', 'sss3', 'a4J1uQzQCasD', 's3_small');
if ($this->db->connect_error) {
$this->error = $this->db->connect_error;
}
return $this->db;
}
}
$db = new Db;
if (isset($db->error)) {
die($db->error);
}
echo 'xxx', PHP_EOL;
Using __isset and __get magic methods
class Db {
private $db;
private $error;
public function __construct() {
$this->db = new mysqli('localhost', 'sss3', 'a4J1uQzQCasD', 's3_small');
if ($this->db->connect_error) {
$this->error = $this->db->connect_error;
}
return $this->db;
}
public function __get($key) {
if ($key === 'error') {
return $this->error;
}
}
public function __isset($key) {
if ($key === 'error') {
return isset($this->error);
}
}
}
$db = new Db;
if (isset($db->error)) {
die($db->error);
}
echo 'xxx', PHP_EOL;
Implementing a getter method
A getter method is just a method returning value of a private member. In our case it is $error. So you might leave it private, but add a method to access its value. For instance:
public function getError() {
return $this->error;
}