Mysqli查询出现额外空记录及foreach异常问题求助

Hey, let's troubleshoot that empty <li> tag and misbehaving foreach loop you're seeing with your MySQLi code!

The Root Cause #

The issue comes from this line of code:

while ($zzmcat[] = $zmcat->fetch_array(MYSQLI_ASSOC)){}

When fetch_array() runs out of rows to return, it returns false. Your current code appends this false value directly to the $zzmcat array. So when you loop through the array later, the last element is an invalid false entry—this causes the empty <li> tag (since $zcatzn["cname"] will be undefined/empty) and throws off your inner loop logic.

Fix 1: Adjust the While Loop Logic #

Rewrite your array population code to only add valid rows to the array:

$zzmcat = array();
// First capture the row, then check if it's valid before adding to the array
while ($row = $zmcat->fetch_array(MYSQLI_ASSOC)) {
    $zzmcat[] = $row;
}

This way, we only append data to $zzmcat when fetch_array() returns a valid associative array (not false).

Fix 2: Simplify with fetch_all() #

If you're running PHP 5.3 or later, you can skip the manual while loop entirely and use fetch_all() to get all results in one go:

$zzmcat = $zmcat->fetch_all(MYSQLI_ASSOC);

This method directly returns an array of all rows, with no extra false element at the end—cleaner and less error-prone.

Bonus: Fix SQL Injection Risk #

Your inner query uses string concatenation for the cat_id parameter (cat_id='".$zcatzn['cid']."'), which is a major SQL injection vulnerability. Replace it with a prepared statement to make your code secure:

// Prepare the inner query once, outside the loop
$q = "SELECT id, ename FROM items WHERE view > 4 and status = 1 and cat_id = ?";
$stmt = $dba->prepare($q);

foreach ($zzmcat as $zcatzn) {
    ?>
    <li class="category-list list-parent"><a href="#"><?php echo $zcatzn["cname"]; ?></a>
        <ul class="list-child">
            <?php
            // Bind the category ID parameter (the "i" denotes an integer type)
            $stmt->bind_param("i", $zcatzn['cid']);
            $stmt->execute();
            $result = $stmt->get_result();
            
            while ($product = $result->fetch_array(MYSQLI_ASSOC)) {
                ?>
                <li class="category-list"><a href="#">
                        <?php echo $product['ename']; ?>
                    </a></li>
                <?php
            }
            ?>
        </ul>
    </li>
    <?php
}

// Clean up the prepared statement
$stmt->close();

These changes should eliminate the empty <li> tag and get your foreach loop working as expected, while also making your code more secure.

内容的提问来源于stack exchange，提问作者Fahad Almehaini