php - How can i test all scenarios of firstname and lastname -

i have function must test scenarios of firstname :

1-first scenarios if firstname empty . 2-second scenarios if firstname contains 1 character. 3-third scenrarios if firstname have 2 character. 4-four scenarios if firstname have 3 character. 5-other scenarios ... 

so here function :

<?php $loginuser = $thirdpartycode .'_'. substr($firstname, 0, 1) .''. substr($lastname, 0, 1); echo 'login user generatedlogin:'. $loginuser;  // $usercheck = new admin_model_dbtable_user(); // $iduser=$usercheck->checkuser($loginuser);  $firstnamex = 0; $firstnamey = 1; $lastnamex = 0; $lastnamey = 1; $max = 4; {     ++$firstnamey;     ++$lastnamey;     if (empty($firstname)) {         $loginuser = $thirdpartycode .'_'. substr($lastname, $lastnamex, $lastnamey);     }     else {         if (strlen($firstname) < $max) {             $firstnamex = 0;             $firstnamey = 1;             $loginuser = $thirdpartycode .'_'. substr($firstname, $firstnamex, $firstnamey) . '' . substr($lastname, $lastnamex, $lastnamey);         }          $loginuser = $thirdpartycode .'_'. substr($firstname, $firstnamex, $firstnamey) . '' . substr($lastname, $lastnamex, $lastnamey);     }      $usercheck = new admin_model_dbtable_user();     $iduser = $usercheck->checkuser($loginuser);     if (($firstnamey == $max) && ($lastnamey == $max)) break; }  while ($iduser > 0); error_log('login user generatedlogin:'. $loginuser); return $loginuser; 

please can script , tell me can update take scenarios.