JavaScript with php variabe isn't working

Question

I'm new to to working with php html and javascript so I apologize if this question is bad but whenever I add this variable that echos php I can no longer advance the program to the next window. The only thing I can think of is that the next window is a html and not a php file. Would that be the reason or am I doing something else wrong? Thanks!

<script>
    var winner = <?php echo $winnerName ?>;
    //Creates random num for winner base on num of members.
    function changeNum() {
        //Num of members.
        num = document.getElementById("num").value;
        //winner.
        num2 = Math.round((Math.random() * (num - 1) + 1));
        //Storage to second page
        localStorage.setItem("winner", num2);
        localStorage.setItem("name", winner);

        window.location = "second_page.html";
    }
</script>

Answer 1

PHP will print out your string in plain text and to the browser it will exactly like if you were to have typed and hardcoded the string held by $winnerName in the file itself.

For example if $winnerName = 'Bob' the browser will see var winner = Bob; and complain that you haven't defined the variable Bob .

Keeping that in mind, there are two methods to make javascript treat your string as a string, and not a variable.

1. var winner = <?php print json_decode($winnerName); ?>;
2. var winner = '<?php print $winnerName; ?>'

Both of which will display to the browser var winner = 'Bob' .

Answer 2

A couple of potential issues:

1. $winnerName is probably a string, which means that you need to wrap it in quotes: '<?=$winnerName;?>' (and probably escape it as well to be on the safe side): '<?=addslashes($winnerName);?>'

2. Make sure that num is a legitimate integer: parseInt(document.getElementById("num").value) just in case that might be throwing an error.

Also, you'll want to look at your console to see what javascript error is being throw - it will narrow down the issue for you.