javascript - Request header field Access-Control-Allow-Headers is not allowed by Access-Control-Allow-Headers in preflight response -

i trying make login page cross domain couldn't solve problem, error is:

xmlhttprequest cannot load http://localhost/testing/resp.php. request header field access-control-allow-headers not allowed access-control-allow-headers in preflight response.

my javascript code is:

$('#login').click(function(){  		var username = $('#uname').val();  		var password = $('#pass').val();  		var result = $('.result');  		result.text('loading....');    		if (username != '' && password !=''){  			var urltopass = 'action=login&username='+username+'&password='+password;  			$.ajax({  				type: 'post',  				data: urltopass,  				headers: {"access-control-allow-headers": "content-type"},  				url: 'http://localhost/testing/resp.php',  				crossdomain: true,  				cache: false,  				success: function(responsetext){  					console.log(responsetext);  					if(responsetext== "0"){  						result.text('incorrect login information');  					} else if (responsetext == "1"){  						window.location="http://localhost/testing/home.php";  					} else{  						alert('error in sql query \n' + responsetext);  					}  				}  			});  		} else return false;  	});

the php code http://localhost/testing/resp.php :

<?php  	include "db.php"; //connecting database    	if (!isset($_server['http_origin'])) {  		echo "this not cross-domain request";      exit;  }  	header("access-control-allow-origin: *");  	header("access-control-allow-credentials: true");  	header("access-control-allow-methods: post, get, options");  	header("access-control-allow-headers: content-type, authorization, x-requested-with");  	header('p3p: cp="cao psa our"'); // makes ie support cookies  	header("content-type: application/json; charset=utf-8");    	if (isset($_post['action']) && $_post['action'] == 'login'){  		$uname = $_post['username'];  		$pass = $_post['password'];    		$sql = "select * loginajax username='$uname' , password='$pass'";  	  		$rs=$conn->query($sql);    		if (mysqli_num_rows($rs) <= 0){  			echo "0";  		} else {  			echo "1";  		}  		  	} else echo "this not login";    ?>

remove this:

headers: {"access-control-allow-headers": "content-type"}, 

from jquery.ajax call.

the server responds access-control-allow-headers header, client doesn't send server.

the client sends access-control-request-headers request allowing headers, server responds with access-control-allow-headers lists actual headers going allow. client not demand headers allowed.