json_encode布尔返回错误的值

I'm writing a jquery login. If the php login script (checklogin.php) echoes "true" then my jquery page is supposed to give an alert. When I run a login.php (that doesn't use jquery) it sends the request to checklogin.php which echoes "true" however if I use my jquery login script to send the login info to checklogin.php, the alert I trace back says "false".

$('#login').click(function(e){
      $.getJSON("http://www.hedonsoft.com/game/login.php",{username: $("#username").val(), password: $("#password").val()},function(data){
         if(data==true){
            alert(data.boolean);
            //$('#logindiv').slideUp();
            //$('#gamediv').show(); 
            //$('#registerdiv').hide();
            //$('#gameheader').html(data['username']);
         }else{
            alert("false");
         }
      });
});

<?php
header('Access-Control-Allow-Origin: *');
$host="localhost"; // Host name 
$username=""; // Mysql username 
$password=""; // Mysql password 
$db_name="hedonsof_conflict"; // Database name 
$tbl_name="members"; // Table name 

// Connect to server and select databse.
mysql_connect("$host", "$username", "$password")or die("cannot connect"); 
mysql_select_db("$db_name")or die("cannot select DB");

// username and password sent from form 
$myusername=$_POST['myusername']; 
$mypassword=$_POST['mypassword']; 

// To protect MySQL injection (more detail about MySQL injection)
$myusername = stripslashes($myusername);
$mypassword = stripslashes($mypassword);
$myusername = mysql_real_escape_string($myusername);
$mypassword = mysql_real_escape_string($mypassword);

$sql="SELECT * FROM $tbl_name WHERE username='$myusername' and password='$mypassword'";
$result=mysql_query($sql);

// Mysql_num_row is counting table row
$count=mysql_num_rows($result);

// If result matched $myusername and $mypassword, table row must be 1 row
if($count==1){

// Register $myusername, $mypassword and redirect to file "login_success.php"
session_register("myusername");
session_register("mypassword"); 
$json = array('boolean' => 'true', 'jsonUser' => $myusername);
echo "true";
}
else {
echo "Wrong Username or Password";
}
?>

So long story short, when I try to login from a regular php page the value I trace is true, when I try to login from a jquery page the value I trace is false;

EDIT:

<?php
...
$sql="SELECT * FROM $tbl_name WHERE username='$myusername' and password='$mypassword'";
$result=mysql_query($sql);

// Mysql_num_row is counting table row
$count=mysql_num_rows($result);

// If result matched $myusername and $mypassword, table row must be 1 row
if($count==1){

// Register $myusername, $mypassword and redirect to file "login_success.php"
session_register("myusername");
session_register("mypassword"); 
$json = array('boolean' => true, 'jsonUser' => $myusername);
echo true;
}
else {
echo "Wrong Username or Password";
}
?>

And my jQuery...

$('#login').click(function(e){
      $.getJSON("http://www.hedonsoft.com/game/login.php",{username: $("#username").val(), password: $("#password").val()},function(data){
         if(data){
            alert("true");
            //$('#logindiv').slideUp();
            //$('#gamediv').show(); 
            //$('#registerdiv').hide();
            //$('#gameheader').html(data['username']);
         }else{
            alert(data); // shows null
         }
      });
});

With json_encode, boolean's value is returned null

$('#login').click(function(e){
       $.getJSON("http://www.hedonsoft.com/game/login.php",{username: $("#username").val(), password: $("#password").val()},function(data){
          if(data.boolean == "true"){
             alert("true");
             //$('#logindiv').slideUp();
             //$('#gamediv').show(); 
             //$('#registerdiv').hide();
             //$('#gameheader').html(data['username']);
          }else{            alert(data);
          }
       }); });

<?php
...
// Register $myusername, $mypassword and redirect to file "login_success.php"
session_register("myusername");
session_register("mypassword"); 
$json = array('boolean' => true, 'jsonUser' => $myusername);
echo json_encode($json);
}
...
?>

Use true, not 'true'. 'true' is a string, and you want a boolean:

$json = array('boolean' => true, 'jsonUser' => $myusername);

Also, never write == true.

if(data==true) {

Okay, now the problem is:

$json = array('boolean' => true, 'jsonUser' => $myusername);
echo true;

Don't echo true, echo json_encode($json).