OOP PHP method doesn't work when invoked within another method - php

Question

I'm creating a PHP class for a Wordpress site. The following method works fine, but when I try to abstract it a bit by passing an argument and calling it within another method (see code further down below), it doesn't work anymore.
public function user_has_submitted_in_dog_category() {
$args = array(
'post_type' => 'submissions',
'author' => get_current_user_id(),
'tax_query' => array(
array(
'taxonomy' => 'submissions_categories',
'field' => 'slug',
'terms' => 'dog'
)
)
);
$user_posts = get_posts( $args );
if( count( $user_posts ) )
return true;
}
This is not working:
public function user_has_submitted_in_dog_category() {
$this->user_has_submitted_in_animal_category( 'dog' );
}
public function user_has_submitted_in_animal_category( $category ) {
$args = array(
'post_type' => 'submissions',
'author' => get_current_user_id(),
'tax_query' => array(
array(
'taxonomy' => 'submissions_categories',
'field' => 'slug',
'terms' => $category
)
)
);
$user_posts = get_posts( $args );
if( count( $user_posts ) )
return true;
}
By not working, I mean that user_has_submitted_in_dog_category() is not returning true. I call it in a template file as follows:
<?php if( $submission->user_has_submitted_in_dog_category() ) : ?>
<div class="msg">You have already submitted.</div>
<?php else : ?>
<div class="msg">You have not submitted yet.</div>
<?php endif; ?>
The block of code prints You have not submitted yet, but I do have posts in my custom taxonomy dog.

Answer 1

You need to return from your first (dog) method.
public function user_has_submitted_in_dog_category() {
return $this->user_has_submitted_in_animal_category( 'dog' );
}

Answer 2

Wordpress might be calling the method statically. You might be best off doing that yourself as the method doesn't seem to need an object instance to work:
public function user_has_submitted_in_dog_category() {
MyClass::user_has_submitted_in_animal_category( 'dog' );
}