<?php
    declare(strict_types = 1);

class WordBoolean {
    private $word = null;
    private $firstRow = ["q","w","e","r","t","y","u","i","o","p"]; //first row of the keyboard
    private $secondRow = ["a","s","d","f","g","h","j","k","l"]; //second row
    private $thirdRow = ["z","x","c","v","b","n","m"];  //third row
    private $counter1 = null;
    private $counter2 = null;
    private $counter3 = null;
    private $bool = false;

    public function wordCheck(string $word) { //checks if the word is written only by keys from one row
        $word = str_split($word ,1);
        for ($i = 0; $i < count($word); $i++) {
            if (in_array($word[$i], $this->firstRow)) {
                $this->counter1 += 1;
            } elseif (in_array($word[$i], $this->secondRow)) {
                $this->counter2 += 1;
            } elseif (in_array($word[$i], $this->thirdRow)) {
                $this->counter3 += 1;
            }
        }
        if ($this->counter1 == count($word)) {
            $this->bool = true;
            return $this->bool;
        } elseif ($this->counter2 == count($word)) {
            $this->bool = true;
            return $this->bool;
        } elseif ($this->counter3 == count($word)) {
            $this->bool = true;
            return $this->bool;
        }
        return $this->bool;
    }
}
$obj = new WordBoolean();
echo $obj->wordCheck('qwemsad'); //the input
?>