PHP MySQL fatal error after moved to real server - php

Question

I have tested my application in localhost and works very well, after I moved to server, the scripts related to MySQL query are die,
class Test {
public function check_duplicate_username($username, $mysqli)
{
$sql = $mysqli->prepare("SELECT username FROM `account` WHERE username=?");
$sql->bind_param('s', $username); // line 44
$sql->execute();
$res = $sql->get_result();
if($res->num_rows !== 0){
return false;
}
return true;
}
public function get_main_cate($mysqli)
{
$sql = $mysqli->query("SELECT name FROM `category` ORDER BY `id` DESC");
if($sql->num_rows > 0){
return $sql;
}else{
return false;
}
}
}
To fetch the result:
$test = new Test;
if(!$test->check_duplicate_username($email, $mysqli)){
$data['error']['email'] = 'email has been used';
}
echo '<select>';
$cat = $test->get_main_cate($mysqli);
while($obj = $cat->fetch_object()){ //line 134
echo '<option>'.$obj->name.'</option>';
}
echo '</select>';
From the error log:
PHP Fatal error: Call to a member function bind_param() on boolean in /path/to/html/root/classes/test.php on line 44
[24-Mar-2016 02:36:26 America/Chicago] PHP Fatal error: Call to a member function fetch_object() on boolean in /path/to/html/root/sign-up.php on line 134
what's wrong with this issue? Is that cause by missing of library in the server? PHP in hosting is Version 5.6.18, whereas in localhost is Version 5.6.19.

Answer 1

The issue seems to be that your database is empty. The error is clear:
Call to a member function fetch_object() on boolean
You tried to call the function fetch_object on a variable of type boolean. The variable on the line is called $cat and is the result of the function $cat = $test->get_main_cate($mysqli);.
Inside that function you are loading all categories and return them. If no categories are found you return false. You have to add a check if $cat is false before trying to iterate over the results, something like
$cat = $test->get_main_cate($mysqli);
if ($cat != false) {
while($obj = $cat->fetch_object()){ //line 134
echo '<option>'.$obj->name.'</option>';
}
}

Answer 2

Instead of checking your that your data exists with !, try using empty(). If I understand the usage correctly, this method should check for all (or most) types of invalid or empty data requests.
According to http://php.net/manual/en/function.empty.php
Returns FALSE if var exists and has a non-empty, non-zero value. Otherwise returns TRUE.
The following things are considered to be empty:
"" (an empty string)
0 (0 as an integer)
0.0 (0 as a float)
"0" (0 as a string)
NULL
FALSE
array() (an empty array)
$var; (a variable declared, but without a value)
Try changing this line:
if(!$test->check_duplicate_username($email, $mysqli))
to
if(empty($test->check_duplicate_username($email, $mysqli)))
If this doesn't work. You may just need to consider a 2-step check to verify data exists. Keep in mind I have not tested this method with your code.
Warning from source:
No warning is generated if the variable does not exist. That means empty() is essentially the concise equivalent to !isset($var) || $var == false.

Answer 3

Try to use this query
$sql = $mysqli->prepare('SELECT username FROM account WHERE username=?');
$sql->bind_param('s', $username); // line 44