Get JavaScript Variable Value in a PHP Variable? - variables

Question

I have this JavaScript function which is getting a value from a select option in HTML:
<script type="text/javascript">
function showUser(str) {
if (str=="") {
document.getElementById("txtHint").innerHTML="";
return;
}
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) {
var str=xmlhttp.responseText;
var splitstr=str.split('||');
document.getElementById("txtHint").innerHTML=splitstr[0];
document.getElementById("txtval").innerHTML=splitstr[1];
}
}
xmlhttp.open("GET","getdetails.php?q="+str,true);
xmlhttp.send();
}
</script>
Now, str is the JavaScript variable I want to take its value and put it into a PHP variable.
I am using this, but it is not working:
$grade = "<script language=javascript>document.write(str);</script>";
echo $grade;
What is the correct way to do this?

Answer 1

PHP runs on a web server, so it will only execute when the page loads. So the above statement will not work as it runs within the function which is called after page load.
To achieve what you want, you can send str to a php file via ajax call and store it in a session variable. & then whenever you need the variable call another ajax function which will retrieve the session value.

Answer 2

You can use jQuery to handle AJAX calls.
Make sure you include this line in your html page.
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js">
</script>
Use the javascript to make your call to PHP and sent your str data.
function uploaddata(str) {
if (str=="") {
document.getElementById("txtHint").innerHTML="";
return;
}
var fd = new FormData();
fd.append('data1', str);
try {
$.ajax({
url: 'dosomething.php',
data:fd,
processData: false,
contentType: false,
type: 'POST',
success: function(data){
var response = $.parseJSON(data);
if (response.code !== '0'){
alert(response.description);
}
else {
alert(response.description);
};
},
error: function(jqXHR, error, errorThrown) {
alert(jqXHR.responseText);}
});
}
catch (ex) {
}
}
At server side create the dosomething.php will make the process you need.
<?php
// get your data at server side
str = $_POST['data1'];
// do processing
// return answer to browser
$ans = ['code' => '0', 'description' => 'Everything are ok'];
echo json_encode($ans);
return;
?>
At your javascript the success portion will be activated and you can use the code and description to build your logic.