<?php

    $numbers = array
    (
       2.5,
       INF,
       -10
    );

    foreach($numbers as $number)
    {
        $number = (int) $number;

        $twoDigits = substr($number, 0, $number < 0 ? 3 : 2);

        var_dump($number, $twoDigits);
    }

int(2)
string(1) "2"
int(0)
string(1) "0"
int(-10)
string(3) "-10"