PHP object-oriented selection sorting example explanation

<!--?php
/**
 * Created by PhpStorm.
 * User: lzh
 * Date: 2018/2/10
 * Time: 下午10:50
 */
class selectionSortData {
    private $var = array();
 
    /**
     * selectionSortData constructor.
     * @param $in
     */
    public function __construct($in)
    {
        if (is_array($in)) {
            $this--->var = $in;
        }
        if (is_numeric($in)) {
            for ($count = 0; $count < $in; $count ++) {
                $random = mt_rand(1, 100);
                array_push($this->var, $random);
                print_r($this->var);
                echo &#39;
&#39;;
            }
        }
    }
 
    public function swap($left, $right) {
        $temp = $left;
        $left = $right;
        $right = $temp;
    }
 
    public function sort() {
        $temp = $this->var[0];
        for ($i = 0; $i < count($this->var); $i ++) {
            if ($this->var[$i] > $temp) {
                $this->swap($temp, $this->var[$i]);
            }
        }
        return $this->var;
    }
}
 
$selection = new selectionSortData(10);
        echo &#39;
&#39;;
        print_r($selection);