Sending a value from an HTML select to PHP with JavaScript

You can use AJAX.

function get_value_js(){
  var xmlhttp;
  var e = document.getElementById("value_select");
  var the_value = e.options[e.selectedIndex].value;
  if (window.XMLHttpRequest)
    {// code for IE7+, Firefox, Chrome, Opera, Safari
    xmlhttp=new XMLHttpRequest();
    }
  else
    {// code for IE6, IE5
    xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
    }
  xmlhttp.onreadystatechange=function()
    {
    if (xmlhttp.readyState==4 && xmlhttp.status==200)
      {
      //Do whatever with xmlhttp.responseText;
      }
    }
  xmlhttp.open("GET","work.php?val="+the_value,true);
  xmlhttp.send();
}

You can use $_GET['the_value'] to grab the value.

You could either send it as an AJAX call if you want to stay on the same page or perform a redirect and pass the value as query string parameter:

window.location.href = '/work.php?value=' + encodeURIComponent(the_value);

You need to enclose the <select> in a <form> tag like so:

<form id="myForm" method="post" action="work.php">
    <select name="value_select">
        <option value="1">Value 1 text</option>
        <option value="2">Value 2 text</option
    </select>
</form>

Please note that i've added value attributes to the <option> tags & added a name attribute to the <select>. Next, you can submit the form in the following way:

function send()
{
    document.getElementById( "myForm" ).submit();
}

Next in work.php:

<?
    $value_select = $_POST[ "value_select" ];
    echo( $value_select );
?>

Use ajax with jQuery

function get_value_js() {
   var the_value =$("#value_select option:selected").val(); 
   $.post('work.php?val='+the_value , function(data) {
        //do whatever you want with the result
   });
}