Countdown JS+PHP, what's wrong?

Question

I'm trying to make this function work but i don't know what's wrong and i'm not really good at js. I want to do call my timer function with number of seconds to countdown from the span id "count".

Example:

<p id="hello">Wait <span id="count">5</span> secs</p>

<?php
echo '<script type="text/javascript">'
   , 'timer(5);'
   , '</script>';
?>
<script>
function timer(tiempo){

  setInterval(function() {
    tiempo--;
    if (tiempo >= 0) {
      span = document.getElementById("count");
      span.innerHTML = tiempo;
    }
    // Display 'counter' wherever you want to display it.
    if (tiempo === 0) {
      window.location.reload();
        clearInterval(tiempo);
    }

  }, 1000);

});
</script>

What's wrong?

Answer 1

Define the function before it's called:

<script type='text/javascript'>
function timer(tiempo){
  setInterval(function() {
    tiempo--;
    if (tiempo >= 0) {
      span = document.getElementById("count");
      span.innerHTML = tiempo;
    }
    // Display 'counter' wherever you want to display it.
    if (tiempo === 0) {
      window.location.reload();
        clearInterval(tiempo);
    }

  }, 1000);

}
</script>
<p id="hello">Wait <span id="count">5</span> secs</p>

<?php
echo '<script type="text/javascript">'
   , 'timer(5);'
   , '</script>';
?>