Ajax POST请求，parseerror

Question

I'm trying to make a web chat room, but when I send a post request to the server, with this code:

var line_count = 0;

$.ajax({
    type: 'POST',
    url: '../scripts/engine.php',
    data: {'method': 'getMsg', 'line_count': line_count},
    dataType: 'json',
    error: function(request, error) {
        alert('Error: '+error);
    },
    success: function(data) {
        $.each(data.messages, function(i, val) {
            $('.messages').append(val);
        });
        line_count = data.srv_count;
    }
});

And:

<?php
$method = $_POST['method'];

switch($method) {
    case 'postMsg':
        $sender = $_SESSION['username'];
        $message = $_POST['message'];
        $time = $_POST['time'];

        fwrite(fopen('chat.txt', 'a'), '<div class="time">[' . $time . ']</div><div class="nickname">' . $sender . '</div>' . $message . "
");
        break;       
    case 'getMsg':
        $log = array();

        if(file_exists('chat.txt')) {
            $usr_count = $_POST['line_count'];
            $srv_msg = explode("
", file('chat.txt'));
            $srv_count = count($srv_msg);

            $log['srv_count'] = $srv_count;

            if($usr_count < $srv_count) {
                $i = 0;

                while(list($key, $val) = each($srv_msg)) {
                    if ($i > $usr_count) {
                        $log['messages'][i] = $val;
                    }
                    $i = $i+1;
                }
            }
        } else {
            $log = false;
        }

        echo json_encode($log);
        break;
}
?>

Then I get this error message from ajax error function: "Error: parseerror". I checked the code many times, but I don't see where's the issue. Thanks in advance

Thanks everybody for the fast answers I checked returned value from the server, and I undertood it was a server-side problem. returnded value:

Warning: explode() expects parameter 2 to be string, array given in X:\wwwoot\scripts\engine.php on line 17
{"srv_count":0}

I just edited my code into:

                $usr_count = $_POST['line_count'];
                $srv_msg = explode("
", file_get_contents('chat.txt'));
                $srv_count = count($srv_msg);

                $log['srv_count'] = $srv_count;

                if($usr_count < $srv_count) {
                    $i = 0;

                    while(list($key, $val) = each($srv_msg)) {
                        if ($i > $usr_count) {
                            $log['messages'][$i] = $val;
                        }
                        $i = $i+1;
                    }
                }

And now It's working fine.

Answer 1

parseerror just means that you're not getting JSON back from the server. It could be PHP throwing an error and printing the error markup before the json.

check the console to see what is actually being returned from the server.

you may alos want to check is_writable() before attempting to write to a file. it could be a simple permissions issue.