<?php
    $i=1;
    while($i<=5) {
        echo "
        <input type='radio' name='rating$i' value='1' id='rating_0'>
        <input type='radio' name='rating$i' value='2' id='rating_1'>
        <input type='radio' name='rating$i' value='3' id='rating_2'>
        <input type='radio' name='rating$i' value='4' id='rating_3'>
        <input type='radio' name='rating$i' value='5' id='rating_4'>
    ";
        echo "<br />";
        $i++;
    }
    ?>

<form name="myForm" action="myAction.php" method="post">
<?php
    $i=1;
    while($i<=5) {
        echo "
        <input type='radio' name='rating$i' value='1' id='rating_0'>
        <input type='radio' name='rating$i' value='2' id='rating_1'>
        <input type='radio' name='rating$i' value='3' id='rating_2'>
        <input type='radio' name='rating$i' value='4' id='rating_3'>
        <input type='radio' name='rating$i' value='5' id='rating_4'>
    ";
        echo "<br />";
        $i++;
    }
    ?>
</form>

while($i<=5) {
    // do something with $_POST["rating$i"]
}

foreach($_POST as $val){
    // do something with $val
}

foreach($_POST as $key => $val){
    if(substr($key, 0, 6) == 'rating'){
        // do something with $val
    }
}

<form action="page.php" action="post">
<?php
    while($i<=5) {
            echo "
            <input type='radio' name='rating$i' value='1' id='rating_0'>
            <input type='radio' name='rating$i' value='2' id='rating_1'>
            <input type='radio' name='rating$i' value='3' id='rating_2'>
            <input type='radio' name='rating$i' value='4' id='rating_3'>
            <input type='radio' name='rating$i' value='5' id='rating_4'>
        ";
            echo "<br />";
            $i++;
        }
?>
</form>

foreach($_POST() as $radioval)
{
echo $radioval;
}

var elements = document.querySelectorAll('input[name="rating$i"]'); //where rating$i is rating1 rating 2 and so on
for (var element in elements)
{
    var value=element.value;
}

var value = rating$i.value;   //rating1 rating2 and so on