PHP - Save a variable's value

Question

I'm new to PHP and met with a little problem.

I think I was previously unclear and we did some changes so let me edit this :

In this part, we work on 2 classes :

First one a Singleton

<?php

class Model {

    private $_handle = null;

    private function __construct()
    {
        $this->_handle = array ('0'=>'2011,2015','1'=>[],'2'=>["man","woman"],'3'=>'21,55');
    }

    public function __clone()
    {

    }

    public static function getInstance()
    {
        static $_instance = null;

        if ($_instance === null) {
            $_instance = new self();
        }

        return $_instance;
    }

    public function getObj()
    {
        return $this->_handle;
    }

public function setObj($value, $index)
    {
        $this->_handle[$index]= $value;
    }

}

And another class which extends from it.

<?php

include "QueryBuilder.php";

class globalModel extends Model
{
    public function valueSettings($type, $val)
{
        switch($type) 
{
            case 'ages':
                $this->setObj($val, 3);
                break;
            case 'sexe':
                $this->setObj($val, 2);
                break;
            case 'countries':
                $this->setObj($val, 1);
                break;
            case 'date':
                $this->setObj($val, 0);
                break;  
        }
    }   

    }

    public function Main()
    {
        $this->valueSettings($_POST['type'],$_POST['value']);
        $value = $this->getInstance()->getObj();
        //Build Query Sentence
//        $QB = new QueryBuilder();
//        $fullQuery = $QB->QueryBuild($_POST['tab'], $value);
//
//        echo $fullQuery;
    }
}

We did many experimentation and we found that since the _construct is being ran over and over again, the array we set at the beginning is being reset as construct is being called. That's why we try to use a Singleton here and I think it should be good.

But here, the code doesn't work at all ...

Without a singleton, the Array gets updated for the last value we give it. But if we call valueSettings again, it'll act as if we never called it before because it'll take the value from __construct again.

So the questions would be, is it good idea to use a Singleton ? If yes why does this code isn't working ? =( If no, how should we set the array the first time ? Outside of a function ?

Answer 1

I am really not sure what you want to achieve with your code, but let me make 2 comments that might help:

1. the dot operator . in PHP is used to concatenate strings. If you want to access members of an object you need to use ->. I am just assuming here, but Its a common mistake if you come from C++, I stumbled over this too :)
2. If you want to work with JSON I recommend using the build in functions json_encode() and json_decode(). Just create an array with your needed elements and use json_encode to convert them to JSON notation. see also http://php.net/manual/de/function.json-encode.php

Answer 2

This is the best guess I have of what you're trying to do:

public function JsonParse($type, $tab, $val, $value)
{
    $onglet = $tab;
    switch($type) {
    case 'age':
        $value[3] = $val;
        break;
    case 'sexe':
        $value[2] = $val;
        break;
    case 'nationalité':
        $value[1] = $val;
        break;
    case 'année':
        $value[0] = $val;
        break;
    }
    $result = array("onglet"=>$onglet, "value"=>$value};
    return $result;
}

Each time you call this function, it inserts $val into the appropriate place in the $value array, and then returns this new array as the value element of the resulting array. So you can do:

$value = array('', '', '', '');
$new = JsonParse('age', $onglet, 10, $value);
$value = new['value'];

The last line updates $value with the new array returned by the function.

If you want to print it as JSON, you can call json_encode in the caller. Never try to create JSON by hand, there are too many special cases you need to deal with -- just use the built-in functions for it.

Answer 3

To create JSON use json_encode. It seems also more practical to delay the conversion to JSON to the moment when all data has been collected, so you should not do the conversion repeatedly in that function.

Your function could also benefit from array_search, instead of using switch.

Finally, since you are interested in a JSON containing both the values and the tab (onglet), it will be practical to have the object structured that way from the beginning:

{ onglet: '', value: ['', '', '', ''] }

Or, in PHP syntax:

(object) Array(
    "onglet" => '',
    "value" => array('','','','')
);

Although you can work with global variables inside functions with the global keyword, I would suggest passing the above suggested object as a by reference argument.

Here is some example code.

function collect(&$obj, $type, $tab, $val)
{
    $obj->onglet = $tab;
    $index = array_search($type, array('année', 'nationalité', 'sexe', 'age'));
    if ($index !== false) { // valid $type:
        $obj->value[$index] = $val;
    }
    return $obj; // not really necessary, as $obj is modified in-place.
}       

// the global object in which to collect the data:
$obj = (object) Array(
    "onglet" => '',
    "value" => array('','','','')
);

// collect the data; we don't use return value:
collect($obj, 'année', 'premier', '2015');
collect($obj, 'nationalité', 'premier', 'FR');
collect($obj, 'sexe', 'premier', 'masculin');
collect($obj, 'age', 'premier', '21');

// convert $obj to JSON:
echo json_encode($obj);

// output: 
//   {"onglet":"premier","value":["2015","FR","masculin","21"]}

Persist data across requests:

Now if you don't have all the information during one request, you probably should use session scope variables.

Let's say every element is added by passing URL arguments type, tab, val, then you can persist the data during the session by using session_start and $_SESSION[]:

session_start();
if (!isset($_SESSION["obj"])) { // first time, initialise:
    $_SESSION["obj"] = (object) Array(
        "onglet" => '',
        "value" => array('','','','')
    );
}

// The session variable might already have data from previous request.
// Add the currently provided arguments to it:
collect($_SESSION["obj"], $_GET["type"], $_GET["tab"], $_GET["val"]);

echo json_encode($_SESSION["obj"]);