<?php 
$b = PASSWORD_BCRYPT;
$hash = password_hash($password, $b);

if(password_verify($inputPassword, $hashFromDb))
    echo 'authenticated';

if(!password_needs_rehash($hashFromDb, $b, ['cost' => 10]))
{
    $newHash = password_hash($password, $b, ['cost' => 10]);
    $db->insert($newHash);
}


password_get_info($hashFromDb); 
/*
[ 
    algo => PASSWORD_BCRYPT
    algoName => 'blowfisha'
    cost => 10
]
*/ 1