Refactor php filter/validation - php

Question

I want to refactor this piece of code, it takes input from a form, then sanitizes the input, then it checks if its empty, or too short. It does this for title, content and tags. It stores an errors encountered in an array called errors.
I want to make a function, something like this:
function validate_input($args)
Except I'm unsure as to how I'm going to implement it, and how it'll build up an error list.
(I know I can use something like PEAR QUICKFORM or php-form-builder-class, so please don't mention 'oh use Class xyz').
$title = filter_input(INPUT_POST, 'thread_title', FILTER_SANITIZE_STRING,
array('flags' => FILTER_FLAG_STRIP_HIGH|FILTER_FLAG_STRIP_LOW ));
$content = filter_input(INPUT_POST, 'thread_content');
$tags = filter_input(INPUT_POST, 'thread_tags');
# title here:
if (is_null($title) || $title == "") # is_null on its own returns false for some reason
{
$errors['title'] = "Title is required.";
}
elseif ($title === false)
{
$errors['title'] = "Title is invalid.";
}
elseif (strlen($title) < 15)
{
$errors['title'] = "Title is too short, minimum is 15 characters (40 chars max).";
}
elseif (strlen($title) > 80 )
{
$errors['title'] = "Title is too long, maximum is 80 characters.";
}
# content starts here:
if (is_null($content) || $content == "")
{
$errors['content'] = "Content is required.";
}
elseif ($content === false)
{
$errors['content'] = "Content is invalid.";
}
elseif (strlen($content) < 40)
{
$errors['content'] = "Content is too short, minimum is 40 characters."; # TODO: change all min char amounts
}
elseif (strlen($content) > 800)
{
$errors['content'] = "Content is too long, maximum is 800 characters.";
}
# tags go here:
if (is_null($tags) || $tags == "")
{
$errors['tags'] = "Tags are required.";
}
elseif ($title === false)
{
$errors['tags'] = "Content is invalid.";
}
elseif (strlen($tags) < 3)
{
$errors['tags'] = "Atleast one tag is required, 3 characters long.";
}
var_dump($errors);

Answer 1

Should be pretty simple if understood your problem correctly and you want to validate and sanitize only those three variables.
function validateAndSanitizeInput(Array $args, Array &$errors) {
//validation goes in here
return $args;
}
In this case the errors array is passed by reference so you'll be able to get the error messages from it after the function has been called.
$errors = array();
$values = validateAndSanitizeInput($_POST, $errors);
//print $errors if not empty etc.
By the way you could replace "is_null($content) || $content == """ with "empty($content)"