php - 计算MySQL行数

我试图计算MySQL数据库中的行数，并使用PHP报告该数字。我已经阅读了所有文档，并且我认为这段代码应该可以正常工作，但是无论我如何尝试，它都会失败。

<?php
session_start();
if ( isset($_SESSION['username']) ) {
    $username = $_SESSION['username'];
    $q = "SELECT * FROM messages WHERE recepiants='$username' AND readcheck='T'";
    $count = mysql_num_rows($q);
?>
<div class="user_info">Logged in as <?php echo $username; ?> | <a href="admin.php">Add a post</a> | <a href="experiment.php">View Posts</a> | <a href="inbox.php">Message Center <?php echo $count; ?> </a> | <a href="logout.php">Log Out</a></div>
<?php } else {?>

该脚本成功报告了$username，但$count没有返回数字。有任何想法吗？我在某处缺少括号或分号吗？

最佳答案

您缺少的是运行实际查询：

<?php
session_start();
if ( isset($_SESSION['username']) ) {
    $username = $_SESSION['username'];
    $q = "SELECT * FROM messages WHERE recepiants='$username' AND readcheck='T'";
    $result = mysql_query($q);
    $count = mysql_num_rows($result);
?>
<div class="user_info">Logged in as <?php echo $username; ?> | <a href="admin.php">Add a post</a> | <a href="experiment.php">View Posts</a> | <a href="inbox.php">Message Center <?php echo $count; ?> </a> | <a href="logout.php">Log Out</a></div>
<?php } else {?>

如果这就是您所需要的，可能最好在查询中运行COUNT：

<?php
session_start();
if ( isset($_SESSION['username']) ) {
    $username = $_SESSION['username'];
    $q = "SELECT COUNT(*) AS Count FROM messages WHERE recepiants='$username' AND readcheck='T'";
    $result = mysql_query($q);
    $result = mysql_fetch_assoc($result)
    $count = $result['Count'];
?>
<div class="user_info">Logged in as <?php echo $username; ?> | <a href="admin.php">Add a post</a> | <a href="experiment.php">View Posts</a> | <a href="inbox.php">Message Center <?php echo $count; ?> </a> | <a href="logout.php">Log Out</a></div>
<?php } else {?>

而且，正如其他人所述，您需要一个活动的数据库连接。

http://www.php.net/manual/en/function.mysql-fetch-assoc.php