如何修复警告：mysql_fetch_array（）期望参数1是资源，布尔值是？ [重复]

Question

Possible Duplicate:
PHP: Warning: sort() expects parameter 1 to be array, resource given

I keep getting the following message Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given in C:\xampp\htdocs\test\test.class.php on line 22 But when i check the code i can't see what is wrong...

<?php
// Main menu items
$sql=mysql_query("SELECT * FROM category WHERE tier='1' ORDER BY id ASC");
while($row = mysql_fetch_array($sql)){      
    $p_id= $row["id"];
    $p_category_name= $row["category_name"];
    $mainMenu[''.$p_category_name.'']= $p_id;

    $sql_1=mysql_query("SELECT * FROM category WHERE tier='2' parent='$p_id' ORDER BY id ASC");
    while($row_1 = mysql_fetch_array($sql_1)){ **This is line 22**
        $c_id= $row_1["id"];
        $c_category_name= $row_1["category_name"];
        $subMenu[''.$p_category_name.''][''.$c_category_name.''] = 'product1.php';
    } 

}

Answer 1

This means mysql_query failed to execute the query, and you should use mysql_error() to see the error message.

In this case, it looks like you're missing an AND:

$sql_1=mysql_query("SELECT * FROM category WHERE tier='2' AND parent='$p_id' ORDER BY id ASC");

(And please look into PDO.)