AJAX $ _POST不起作用，而$ _REQUEST起作用

Question

When I try to use AJAX POST, the following html doesn't work.

<script>
function call_hmm_scan() {
var specie = document.getElementById("specie_name").value;
var loci = document.getElementById("locus_id").value;

var params="specie_name=" + specie + "&locus_id=" + loci

    var xmlhttp = new XMLHttpRequest();

    xmlhttp.onreadystatechange = function() {
        if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
            document.getElementById("domains").innerHTML = xmlhttp.responseText;
        }
    };

//        xmlhttp.open("GET", "http://shenlab.sols.unlv.edu/kwatanabe/ajax_test.php?" + params, true);
//        xmlhttp.send();

    xmlhttp.open("POST", "http://shenlab.sols.unlv.edu/kwatanabe/ajax_test.php", true);
    xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    xmlhttp.send(params);
}
</script>

My PHP code in "ajax_test.php" is as follows:

<?php
$specie = $_POST["specie_name"];
$loci = $_POST["locus_id"];
echo("$specie<br>");
echo("$loci");
?>

When I uncomment out the GET lines in my HTML, and change $_POST to $_REQUEST in my PHP, it works!!

xmlhttp.open("GET", "http://shenlab.sols.unlv.edu/kwatanabe/ajax_test.php?" + params, true);
xmlhttp.send();

Why doesn't POST work?

Answer 1

The problem is because of this line,

xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");

xhttp is not defined in your code.

So, change

xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");

to

xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");