PHP OOP, MYSQLi Query

Question

I have created a class named "Connection" for DB queries:

class Connection{
 public $mysqli;

 public function read($query){  
  $result= $this->mysqli->query($query);

  $num_result=$result->num_rows;

  if($num_result>0){
   while($rows=$result->fetch_assoc()){

    $this->data[]=$rows;
  }          
   return $this->data;
  }
 }
}

This is how I'm calling my class:

$obj=new Connection("localhost","root","","testpaginate");

$query="SELECT * FROM paginate";
$result=$obj->read($query);
mysqli_free_result($result);

$queries="SELECT * FROM paginate where id=1";
$results=$obj->read($queries);
print_r($results);
?>

When I execute

$query="SELECT * FROM paginate";
$result=$obj->read($query);

it shows the right answer.

When I again execute

$queries="SELECT * FROM paginate where id=1";
$results=$obj->read($queries);

it shows current result with previous result

Why so? Any help is much appreciated.

because you reuse $this->data[] and append your data there. just set $this->data = array(); before you fill it; — Raphael Müller
– Raphael Müller, Commented Mar 4, 2015 at 13:52

Tom Fenech · Accepted Answer · 2015-03-04 14:05:45Z

2

It's a good practice to declare variables correct in your classes.

You should do this every time you use them (if not used for other purposes):

class Foo {
    private $data;

    public function read()
    {
        $this->data = array();

        //do your stuff here, i.e. in your loop
        while(...)
           $this->data[] = $row;

        return $this->data;
    }
}

There could also be the possibility where you don't want to have a private variable associated:

class Foo {

    public function read()
    {
        $data = array();

        //do your stuff here, i.e. in your loop
        while(...)
           $data[] = $row;

        return $data;
    }
}

Now $data is just a local variable.

edited Mar 4, 2015 at 14:05

Tom Fenech

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answered Mar 4, 2015 at 13:57

Raphael Müller

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Comments

Tom Fenech · Accepted Answer · 2015-03-04 13:54:21Z

2

The issue is that you're appending to $this->data every time you call read. You need to reinitialise the array $this->data in the method:

if($num_result>0){
    $this->data = array();
    while($rows=$result->fetch_assoc()){
        $this->data[]=$rows;
    }
}

answered Mar 4, 2015 at 13:54

Tom Fenech

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Comments

Sjoerd · Accepted Answer · 2015-03-04 13:53:13Z

-3

I think you should not use the [] after $this->data. It means it will add rows to the array.

answered Mar 4, 2015 at 13:53

Sjoerd

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1 Comment

jeroen Over a year ago

Sorry, but that's wrong, now the property will contain only the last row of the query.

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