<style>
    div{
        background-color: blue;
    }

    div:nth-child(odd){
        background-color: red;
    }
</style>

<?php
$cars = ['car','car','car','car','car','car','car','car','car','car','car'];

$i = 0;

echo "<div>";
foreach($cars as $car){
    echo $car . "<br />";
    $i++;
    if($i > count($car) / 2){
        echo "</div><div>";
        $i = 0;

    }
}

echo "</div>";
?>