<?php

$arr = array(

    0.10 => 'true'

);

foreach ($arr as $key => $val) {
    var_dump($key);
    if (is_int($key)) {
        echo 'is int';
    }
    echo "\n";
    if (is_numeric($key)) {
        echo 'is numeric';
    }
}

?>

int(0)
is int
is numeric