Finde ikke-eksisterende værdi i $array

<?php

$array = array(
    0 => 0.50,
    10 => 0.53,
    20 => 0.57,
    30 => 0.64,
    40 => 0.70,
    50 => 0.76,
    60 => 0.81,
    70 => 0.85,
    80 => 0.89,
    90 => 0.92,
    100 => 0.94,
    101 => 0.96);

$var = rand(1,200);
$key = ( $var < 100 ? ceil( $var / 10) * 10 : 101);

echo $var.'<br>';
echo $array[$key];

?>

<?php

$array = array(
    0 => 0.50,
    10 => 0.53,
    20 => 0.57,
    30 => 0.64,
    40 => 0.70,
    50 => 0.76,
    60 => 0.81,
    70 => 0.85,
    80 => 0.89,
    90 => 0.92,
    100 => 0.94,
    101 => 0.96);

function FindNearest($search, $array) {
    $nearest = NULL;
    $last_key = array_shift( array_keys( $array, end($array)));
    if( $search <= $last_key) { 
        foreach($array as $key => $value) {
            if( $search <= $key) {
                $nearest = $key;
                break;
            }
        }
    }
    else {
        $nearest = $last_key;
    }
    return $array[$nearest];
}

$var = rand(1,200);

echo $var.' - '.FindNearest( $var, $array);

?>