来自表单的数组值

I have a form which contains up to 10 sets of radio buttons. The radio button provides an answer to a question. All questions are populated from a database and on completion, the database is updated with the fields user_id, question_number & answer_value. I am using an array but only one answer_value seems to pass to the form processor.

This is my code

    <form action="new-answers.php" method="post" id="my_answer">    
    <div class="form-group">
    <label class="radio-inline"><input name="answer_value[]" type="radio" required="required" value="1">&nbsp;Totally false for me&nbsp;</label>
    <label class="radio-inline"><input name="answer_value[]" type="radio" required="required" value="2">&nbsp;Partially false for me&nbsp;</label>
    <label class="radio-inline"><input name="answer_value[]" type="radio" required="required" value="3">&nbsp;Indifferent/neutral&nbsp;</label>
    <label class="radio-inline"><input name="answer_value[]" type="radio" required="required" value="4">&nbsp;Partially true for me&nbsp;</label>
    <label class="radio-inline"><input name="answer_value[]" type="radio" required="required" value="5">&nbsp;Totally true for me&nbsp;</label>

This is what I'm using in the form processor page

if (isset($_POST['submit'])) {
$i=0;

$user=$_POST['user_id'];
$question=$_POST['question_number'];
$answer = $_POST['answer_value']; 
// open the mysqli prepared statement globally
$stmt = $mysqli -> prepare('INSERT INTO answers (user_id,question_number,answer_value) VALUES (?, ?,?)');

function insertAnswer($user, $question, $answer) {
    global $stmt;

    // using prepared statement several times with different variables
    if (
        $stmt &&
        $stmt -> bind_param('iii', $user, $question,$answer) &&
        $stmt -> execute()
    ) {
        // new answers added
    }

}
}

Even when I try just echoing using

$answer = $_POST['answer_value'];

foreach($answer as $value) {
    echo $value.'<br />';
}

I get only answer.