<?php
$sum = [];

for($n = 10; $n <= 99; $n++)
{
    for($d=$n+1;$d <= 99; $d++)
    {
        foreach([1,2,3,4,5,6,7,8,9] as $digit) 
        {
            $ns = (int)str_replace($digit, '', $n);
            $ds = (int)str_replace($digit, '', $d);

            if($n != $ns && $d != $ds && $d != 0 && $ds != 0) 
            {
                if($n/$d == $ns/$ds)
                {
                    echo "$n/$d = $ns/$ds\n";
                    $sum[] = $ns/$ds;
                }
            }
        }
    }
}
echo array_product($sum).PHP_EOL;