Wordpress functions not available in template - php

Question

I am editing front-page.php and there I use get_posts() to output posts.
The other ways like using the_post are not working. So I need to output excerpt, but $post->post_excerpt is empty and the_excerpt function does nothing. I don't understand why, cause there are no errors. Here is the code:
<?php
foreach ( get_posts() as $post ) { ?>
<article id="post-<?php the_ID(); ?>" <?php post_class('article-item well'); ?>>
<h2 class="title text-primary">
<a href="<?php echo $post->guid; ?>">
<?php echo $post->post_title; ?>
</a>
</h2>
<p class="article-info text-center">
<span class="date">Posted on <time pubdate="" title="12:19 pm" datetime="<?php echo $post->post_date; ?>" class="time">
<?php echo $post->post_date; ?>
</time>
</span>
</p>
<?php if (has_post_thumbnail()) { ?>
<figure class="img-wrap">
<?php the_post_thumbnail('full'); ?>
<figcaption class="label label-primary">
<?php foreach((get_the_category()) as $category) {
echo $category->cat_name . ' ';
} ?>
</figcaption>
</figure>
<?php } ?>
<p>
<?php the_excerpt(); ?>
</p>
BTW the_ID function is working and outputs post's id properly.

Answer 1

On each iteration of the loop you need to 'setup' post data, you do this using setup_postdata( $post );
Amend your code as follows:
<?php
foreach ( get_posts() as $post ) {
setup_postdata( $post );
?>
<article id="post-<?php the_ID(); ?>" <?php post_class('article-item well'); ?>>
<h2 class="title text-primary">
<a href="<?php echo $post->guid; ?>">
<?php echo $post->post_title; ?>
</a>
</h2>
<p class="article-info text-center">
<span class="date">Posted on <time pubdate="" title="12:19 pm" datetime="<?php echo $post->post_date; ?>" class="time">
<?php echo $post->post_date; ?>
</time>
</span>
</p>
<?php if (has_post_thumbnail()) { ?>
<figure class="img-wrap">
<?php the_post_thumbnail('full'); ?>
<figcaption class="label label-primary">
<?php foreach((get_the_category()) as $category) {
echo $category->cat_name . ' ';
} ?>
</figcaption>
</figure>
<?php } ?>
<p>
<?php the_excerpt(); ?>
</p>