chodathedread on "get post thumbnail Sensei woothemes?"

`public function display_courses( $courses = array() ){ ?>
<ul>
<?php

foreach ($courses as $course) {
the_post_thumbnail( $size, $attr );
$post_id = absint( $course->ID );
$post_title = $course->post_title;
$user_info = get_userdata( absint( $course->post_author ) );
$author_link = get_author_posts_url( absint( $course->post_author ) );
$author_display_name = $user_info->display_name;
$author_id = $course->post_author;
?>

<li class="last_output col-md-3">

<?php function the_post_thumbnail( $size = 'post-thumbnail', $attr = '' ) {
echo get_the_post_thumbnail( null, $size, $attr );
} ?>

<br />

<a href="<?php echo esc_url( get_permalink( $post_id ) ); ?>"
title="<?php echo esc_attr( $post_title ); ?>">

<?php echo $post_title; ?>

</a>
<br />

<?php if ( isset( Sensei()->settings->settings[ 'course_author' ] ) && ( Sensei()->settings->settings[ 'course_author' ] ) ) { ?>
<span class="course-author">
<?php _e( 'by ', 'woothemes-sensei' ); ?>
<a href="<?php echo esc_url( $author_link ); ?>" title="<?php echo esc_attr( $author_display_name ); ?>">
<?php echo esc_html( $author_display_name ); ?>
</a>
</span>
<br />
<?php } // End If Statement ?>

<span class="course-lesson-count">
<?php echo Sensei()->course->course_lesson_count( $post_id ) . ' ' . __( 'Lessons', 'woothemes-sensei' ); ?>
</span>

<br />

<?php sensei_simple_course_price( $post_id ); ?>

</li>

<?php
} // End For Loop

if ( 'activecourses' == esc_attr( $this->instance['component'] ) || 'completedcourses' == esc_attr( $this->instance['component'] ) ) {
$my_account_page_id = intval( Sensei()->settings->settings[ 'my_course_page' ] );
echo '<li class="my-account fix"><a href="'. esc_url( get_permalink( $my_account_page_id ) ) .'">'
.__('My Courses', 'woothemes-sensei')
.'<span class="meta-nav"></span></a></li>';
} // End If Statement

?>
</ul>

<?php }