find_unique_value_in_table.php

<?php
    function is_unique
    (
        $db = null
    )
    {
        // this statement means please count, and tell me how many students have rollnumber = 1022
        $count = $db->count("students",["student_rollnumber"=>"1022"]);
        // if count == 0 means no student has rollnumber 1022
        if($count == 0) {
          return true; // yes it is unique
        } else {
          // else means there is 1 or more student who have rollnumber 1022 which means it is not unique
          return false; // no it is not unique
        }
    }
    // using library medoo for mysql
    // website http://medoo.in/