PHP Error Gathering Database Information - php

Question

Hi I have the following code below in a php file
global $server, $mysqlusername, $mysqlpassword, $db;
$conn = new mysqli($server, $mysqlusername, $mysqlpassword, $db);
function getCategories() {
global $conn;
$categories = array();
$sql = "SELECT categoryName FROM reportcategorys";
$maincat = $conn->query($sql);
while($row = $maincat->fetch_array(MYSQLI_ASSOC)) {
// do something with the $row
array_push($categories, $row);
}
$sql1 = "SELECT * FROM reportsubcategorys";
$subcats = $conn->query($sql1);
// Loop through sub categories and append to parent array
while($row = $subcats->fetch_array(MYSQLI_ASSOC)) {
$parent = $row['categoryName'];
$name = $row['subCategoryName'];
// Append subcategory name as child to the parent category
for ($i=0; $i<count($categories); $i++) {
if ($categories[$i]['categoryName'] == $parent) {
array_push($categories[$i], $name);
}
}
}
//print_r($categories);
return $categories;
}
It is giving me an error message saying
"Fatal error: Call to a member function fetch_array() on a non-object in"
Any idea what may be causing this?
Thanks

Answer 1

It is likely that your query has not executed properly.
mysqli->query() will return a boolean value FALSE if the query has not been executed properly, else it will return a mysqli_result object. So after every query, before calling fetch_array() method, check the result of the query. Something like this.
$maincat = $conn->query($sql) or die($conn->error);
or
$maincat = $conn->query($sql);
if(!$maincat){
echo $conn->error;
}
Also, when you established your connection with the database, check if the connection was error-free.
if ($conn->connect_errno) {
printf("Connect failed: %s\n", $conn->connect_error);
exit();
}

Answer 2

Are you using fetch_array for any reason in particular?
Try it like this one...
<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");
/* verificar la conexión */
if (mysqli_connect_errno()) {
printf("Conexión fallida: %s\n", mysqli_connect_error());
exit();
}
$query = "SELECT Name, CountryCode FROM City ORDER by ID DESC LIMIT 50,5";
if ($result = $mysqli->query($query)) {
/* obtener array asociativo */
while ($row = $result->fetch_assoc()) {
printf ("%s (%s)\n", $row["Name"], $row["CountryCode"]);
}
/* liberar el resultset */
$result->free();
}
/* cerrar la conexión */
$mysqli->close();
?>