[jQuery] function $.ajax return true/false ?

[jQuery] function $.ajax return true/false ?


Hello
I have the following code:
function pnrexists(a){
    $.ajax({
        url: '/inc/chkusr.php?q=p',
        type: 'POST',
        dataType: 'html',
        data: {'pnr': a},
        timeout: 2000,
        success: function(data) {
            if(data==1){
                alert('true');
                return true;
            }else{
                alert('false');
                return false;
            }
        },
    });
}
the code above is triggered by:
$.validator.addMethod("pnrcheck", function(ph, element) {
    alert('1');
    if(persnr(ph)) {
        alert('2');
        if(pnrexists(ph)) {
        alert('3');
the code continues..but noting to show...
The problem is: I see:
alert 1
alert 2
alert true
but NOT alert 3?? Why?