Call to undefined function sanitize() - php

Question

I'm working on an e-commerce project, currently on back end on the project where you can add or remove menus or sub-menues of categories .
I have checked dlls are enabled
That's the error I'm getting
Fatal error: Call to undefined function sanitize() in C:\xampp\htdocs\project\admin\categories.php on line 15
Here is the code
<?php
require_once $_SERVER['DOCUMENT_ROOT'].'/project/core/init.php';
include 'includes/head.php';
include 'includes/navigation.php';
$sql = "SELECT * FROM categories WHERE parent = 0";
$result = $db->query($sql);
$errors = array();
// when the form is cick process
$Category = '';
$parent= '';
if(isset($_POST) && !empty($_POST)){
$parent = sanitize($_POST['parent']);
$category = sanitize($_POST['category']);
$sqlform = "SELECT * FROM categories WHERE category ='$category' AND parent = '$parent'";
$fresult = $db->query($sqlform);
$count = mysqli_num_rows($fresult);
//if category is blank
if($category == ''){
$errors[] .= 'The category cannot be left blank';
}
//if it already exixt in database
if($count > 0){
$errors[] .= $category.' Already exits please choose a new category';
}
//display error or update database
if(!empty($errors)){
$display = display_errors($errors);?>
<script>
jQuery('document').ready(function(){
jQuery ('#errors').html('<?php $display;?>');
});
</script>
<?php } else{
//update database
$updatesql = "INSERT INTO categories(category,parent)VALUES ('$category','$parent')";
$db->query($updatesql);
header('location:categories.php');
}
}
?>

Answer 1

It seems to me that, sanitize isn't defined in scope. It's not a standard function so it should be somewhere within your code. You can most likely substitute it directly with mysqli_real_escape_string like this:
$parent = mysqli_real_escape_string($_POST['parent']);
$category = mysqli_real_escape_string($_POST['category']);
You should use PDO instead, that would be much better!
Hope this helps!