Problem in calling static and non static method

[Mhari]

Hi,

I dont know what title that is more suitable for this topic but I will try to explain it as well as I can

I have a class that I will use it for interacting with database

I facing a problem when calling the method with "::" assign

here is the code

<?php

class Crud
{
    protected $data;
    protected $db;
    protected $query;
    protected static $action;
    protected static $instance = null;
    protected static $columns  = [];
    protected $table;

    public function __construct()
    {
        $this->db = new mysqli('localhost', 'root', '', 'bahan_belajar');
        if (!$this->db) {
            // throw new Exception("Koneksi error", $this->db->errno);
            echo "error";
        }
        return $this;
    }

    public static function getInstance()
    {
        if (self::$instance === null) {
            self::$instance = new self;
        }
        return self::$instance;
    }

    public function select()
    {
        if (empty(func_get_args())) {
            // $this->columns = "*";
            self::$columns = "*";
        } else {
            if (is_array(func_get_args())) {
                // self::columns = join(', ', func_get_args());
                self::$columns = join(', ', func_get_args());
            } else {
                // self::columns = func_get_args();
                self::$columns = func_get_args();
            }
        }

        self::$action = "SELECT";
        return $this;
    }

    public function from($tableName)
    {
        $this->table = ' FROM ' . $tableName;
        return $this;
    }

    public function get($getName = 'object')
    {
        $this->query = self::$action . ' ' . self::$columns . ' ' . $this->table;
        switch ($getName) {
            case 'object':
                $this->data = $this->db->query($this->query)->fetch_object();
                break;
            case 'array':
                $this->data = $this->db->query($this->query)->fetch_array();
                break;
            case 'count':
                $this->data = $this->db->query($this->query)->num_rows;
                break;
        }
        return $this->data;
    }
}

$chat = Crud::getInstance()->select('nama', 'teks')->from('chat')->get();


echo '<pre>';
print_r($chat);
echo '</pre>';

actually this code was work fine when I put getInstance() method in the first method but how to make it work without putting that method?

example :

$chat = Crud::select('nama', 'teks')->from('chat')->get();

this will produce Fatal error like :

Fatal error: Uncaught Error: Using $this when not in object context in C:\xampp\htdocs\bahan_belajar\chat\classes.php:47 Stack trace: #0 C:\xampp\htdocs\bahan_belajar\chat\classes.php(74): Crud::select('nama', 'teks') #1 {main} thrown in C:\xampp\htdocs\bahan_belajar\chat\classes.php on line 47

I just want to call it with "::" assign and not with "->" assign in first the method

please help me how to solve this

also I am sorry for my bad code structures 

thanks in advance 

[Don E]

Function select is not defined as a static method. PHP gave the error because select is not a static method and when trying to access a non static method, you need to create an object for it, for that class to access that method. When not, like in your code,  you're using $this as a non object resulting in the fatal error. 

getInstance is a static function thus why it worked. 

[Mhari]

Quote

you need to create an object for it, for that class to access that method.

can you please give me an example on how I applying this to my code?

[iwato]

You appear to have two choices:

1) Redefine your method  as static -- namely,

public static function select() {...}

2) Access your method via a Crud object.

$crud_obj = new Crud();
$crud_obj->select(...);

 

Edited December 10, 2017 by iwato
Better clarity.

[justsomeguy]

I just want to call it with "::" assign and not with "->" assign in first the method

Why?  Why is that important to you?  There are reasons why the class is set up that way (even though it could be set up in a better way), so what reasons do you have for not wanting it that way?