Not getting desired output from PHP class

Question

This is my very first question actually. I am under a learning process of OOP PHP and trying to design my first class for Category. Here is my code

<?php
class category{

public  $catid;
public $datacol;

    public function __construct($catid=0)
    {
        $this->catid=0;
        $this->datacol=$this->load($catid);         
    }

    public function load($catid)
    {
        global $conn;
        $sql=' select * '
            .' FROM tbl_categories'
            .' WHERE catid='.$catid;
        if (!($res=mysqli_query($conn,$sql)) || !mysqli_num_rows($res)>0) 
            return false;
        $this->datacol = mysqli_fetch_array($res);
        $this->catid = $this->datacol['catid'];
        return true;
    }

    public function reload() {
        return $this->load($this->getId());
    }

    /* ------------------> Getter methods <--------------------- */
    public function getId() { return $this->catid; }
    public function getName() { return $this->datacol['category']; }
    public function getOneliner() { return $this->datacol['categoryoneliner']; }
    public function getBrief() { return $this->datacol['categorybrief']; }
    public function getThumb() { return $this->datacol['timg']; }
    public function getImage() { return $this->datacol['limg']; }
    public function getParentID() { return $this->datacol['parentcat']; }
    public function getPagetitle() { return  $this->datacol['catpagetitle']; }
    public function getKeywords() { return $this->datacol['catkeywords']; }
    public function getMetadesc() { return $this->datacol['categorymetadesc']; }
    public function getPriority() { return $this->datacol['priority']; }
    public function getRemarks() { return ($this->datacol['remarks']); }
    public function getRow() { return $this->datacol; }

}

?>

Now, When i create its object from other file with a code as below:

$cat=new category(10);
echo var_dump($cat);
echo var_dump($cat->getId());
echo var_dump($cat->getName());

The output gives me the correct catid when called getID(). But Shows NULL for getName() or any other function other than getID().

What am i doing wrong?

Thanks in advance

`print_r($this->datacol)` and see what fields do you have there — u_mulder, Jan 09 '18 at 11:08
@u_mulder echo $cat->datacol; // shows nothing... and var_dump of the same shows NULL — Neil, Jan 09 '18 at 11:13
In your `constructor` you are setting `datacol` with the result of your `load` function but in the same function you are setting the value of `datacol` already. — Arnold Gandarillas, Jan 09 '18 at 11:15
Should `$this->catid=0;` be `$this->catid=$catid`; in your constructor? — brombeer, Jan 09 '18 at 11:19
ok... i think there is nothing being loaded in datacol .... as i print the following echo var_dump($cat->datacol); It shows the output as below: bool(true) .... So how do i get it to work? — Neil, Jan 09 '18 at 11:24

score 1 · Accepted Answer · answered Jan 09 '18 at 11:28

As @Arnold Gandarillas said, you are overwriting $datacol in the constructor.

Your constructor calls load(), which sets $datacol:

public function load($catid)
{
    ...
    $this->datacol = mysqli_fetch_array($res);
    return true;
}

The function then returns true. In the constructor, this true is assigned to $datacol, overwriting the previous value:

public function __construct($catid=0)
{
    $this->catid=0;
    $this->datacol=$this->load($catid);         
}

Change the constructor to something like this:

public function __construct($catid=0)
{
    if ($catid > 0)
        $this->load($catid);         
}

score 0 · Answer 2 · answered Jan 09 '18 at 11:27

Alright - look closely to your function:

public function load($catid)
{
    global $conn;
    $sql=' select * '
        .' FROM tbl_categories'
        .' WHERE catid='.$catid;
    if (!($res=mysqli_query($conn,$sql)) || !mysqli_num_rows($res)>0) 
        return false;
    $this->datacol = mysqli_fetch_array($res);
    $this->catid = $this->datacol['catid'];
    return true;
}

So, you function returns either true of false. And this boolean values is assgined to $this->datacol here:

$this->datacol = $this->load($catid);

As this assignment happens after you did $this->datacol = mysqli_fetch_array($res);, your $this->datacol becomes either true or false, and holds no real data from mysql.

So, one of the solutions can be to remove assignment:

public function __construct($catid=0)
{
    $this->catid=0;
    $this->load($catid);         
}

In this case your $this->datacol is not overwritten.

Thanks for your help! Worked :) Getting my first ever php class to work — Neil, Jan 09 '18 at 11:36

score 0 · Answer 3 · answered Jan 09 '18 at 11:30

its simple $this->datacol = $this->load($catid); is not required

you have assigning $this->datacol twice

 public function __construct($catid=0)
    {
        $this->catid=0;
        $this->load($catid);         
    }
public function load($catid)
{
    global $conn;
    $sql=' select * '
        .' FROM tbl_categories'
        .' WHERE catid='.$catid;
    if (!($res=mysqli_query($conn,$sql)) || !mysqli_num_rows($res)>0) 
        return false;
    $this->datacol = mysqli_fetch_array($res);
    $this->catid = $this->datacol['catid'];
    return true;
}

please add if anything is missing

Not getting desired output from PHP class

3 Answers3