<?php

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

    foreach($numbers as $number)
    {
        $twoDigits = substr($number, 0, 2);

        var_dump($number, $twoDigits);
    }

float(2.5)
string(2) "2."
float(INF)
string(2) "IN"
int(-10)
string(2) "-1"