Looking for existing values in Google Sheet

sheet.php

<?php 

$get= $service->spreadsheets_values->get(SHEET_ID, 'A1:A');
$emails = $get->values;

for($i = 0; $i < count($emails); $i++) {
   if($emails[$i][0] === $email_two) {
      $is_duplicate = true;
      $range = "A".++$i.":H";
      break;
   }
}