Question : Php related question

hello dear experts, i have here some php code and there are some lines that i do not understand.

1. What does this line do?
$qrrystring = '?'.preg_replace('/&page=([0-9])+/','',$qrrystring).'&';

2. What does this line do?
$obj1 = new F1();

3. what does this code do?
            if(isset($myrekest['PHPSESSID']))
            {
            unset($myrekest['PHPSESSID']);
            }
            if(isset($myrekest['__utmz']))
            {
                  unset($myrekest['__utmz']);
            }
            if(isset($myrekest['__utma']))
            {
                  unset($myrekest['__utma']);
            }
            if(isset($myrekest['__utmc']))
            {
                  unset($myrekest['__utmc']);
            }
            if(isset($myrekest['__utmb']))
            {
                  unset($myrekest['__utmb']);
            }

Thank you

Answer : Php related question

1. Replaces the 'querystring' in a URL with &page=([0-9])+

2. Creates a 'new' object of the class F1.

3. 'Unsets' or makes null a series of cookie values.