致命错误：无法将字符串偏移量用作数组

Question

Fatal error: Cannot use string offset as an array in C:\\xampp\\htdocs\\includes\\categories\\categories.php on line 12

$categories[$parent][] = $row;

categories.php

    <?php

$sql = "SELECT catid, catname, parentid FROM categories";
$res = mysql_query($sql);
while ($row = mysql_fetch_assoc($res)) {
    $parent = intval($row['parentid']);
    if (!isset($categories[$parent])) {
        $categories[$parent] = array();
    }
    $categories[$parent][] = $row;
}
    ?>
    <table border="0" cellpadding="10" cellspacing="0">
    <tr>
        <td valign="top">
    <?php
    $category_string = "";
    function build_categories_options($parent, $categories, $level) {
        global $category_string;
        if (isset($categories[$parent]) && count($categories[$parent])) {
            $level .= " - ";
            foreach ($categories[$parent] as $category) {
                $opt_value = substr($level.$category['catname'],3);
                $category_string .= '<option value=""></option><option value="'.$category['catid'].'">'.$opt_value.'</option>';
                build_categories_options($category['catid'], $categories, $level);
            }
            $level = substr($level, -3);
        }
        return $category_string;
    }
    $category_options = build_categories_options(0, $categories, '');
    $category_options = '<select class="chosen" name="categories" id="categories">'.$category_options.'</select>';
    echo $category_options; 
    ?>
</td>

After I insert post With category This Error Will Show ??

Answer 1

I don't see where $categories is initialized, but I'm betting that it's not an array when you enter your while loop, and that's why you're getting an error. Try doing this for your while loop:

// initialize $categories to make sure it is an array
$categories = array();
while ($row = mysql_fetch_assoc($res)) {
    $parent = intval($row['parentid']);
    $categories[$parent][] = $row;
}

You don't need to explicitly initialize $categories[$parent] ...this will be done automatically when you call $categories[$parent][] = $row; . We know that it will start out blank because we started with an empty array before the loop.