Lista os posts com valor de custom field especificado.

multiple_custom_field.php

<?php 

// args
$args = array(
	'numberposts'	=> -1,
	'post_type'		=> 'event',
	'meta_query'	=> array(
		'relation'		=> 'AND',
		array(
			'key'		=> 'location',
			'value'		=> 'Melbourne',
			'compare'	=> '='
		),
		array(
			'key'		=> 'attendees',
			'value'		=> 100,
			'type'		=> 'NUMERIC',
			'compare'	=> '>'
		)
	)
);


// query
$the_query = new WP_Query( $args );

?>
<?php if( $the_query->have_posts() ): ?>
	<ul>
	<?php while ( $the_query->have_posts() ) : $the_query->the_post(); ?>
		<li>
			<a href="<?php the_permalink(); ?>">
				<img src="<?php the_field('event_thumbnail'); ?>" />
				<?php the_title(); ?>
			</a>
		</li>
	<?php endwhile; ?>
	</ul>
<?php endif; ?>

<?php wp_reset_query();	 // Restore global post data stomped by the_post(). ?>

multiple_values.php

<?php 

// args
$args = array(
	'numberposts'	=> -1,
	'post_type'		=> 'event',
	'meta_query'	=> array(
		'relation'		=> 'OR',
		array(
			'key'		=> 'location',
			'value'		=> 'Melbourne',
			'compare'	=> 'LIKE'
		),
		array(
			'key'		=> 'location',
			'value'		=> 'Sydney',
			'compare'	=> 'LIKE'
		)
	)
);


// query
$the_query = new WP_Query( $args );

?>
<?php if( $the_query->have_posts() ): ?>
	<ul>
	<?php while ( $the_query->have_posts() ) : $the_query->the_post(); ?>
		<li>
			<a href="<?php the_permalink(); ?>">
				<img src="<?php the_field('event_thumbnail'); ?>" />
				<?php the_title(); ?>
			</a>
		</li>
	<?php endwhile; ?>
	</ul>
<?php endif; ?>

<?php wp_reset_query();	 // Restore global post data stomped by the_post(). ?>

single.php

<?php 

// args
$args = array(
	'numberposts'	=> -1,
	'post_type'		=> 'event',
	'meta_key'		=> 'location',
	'meta_value'	=> 'Melbourne'
);


// query
$the_query = new WP_Query( $args );

?>
<?php if( $the_query->have_posts() ): ?>
	<ul>
	<?php while( $the_query->have_posts() ) : $the_query->the_post(); ?>
		<li>
			<a href="<?php the_permalink(); ?>">
				<img src="<?php the_field('event_thumbnail'); ?>" />
				<?php the_title(); ?>
			</a>
		</li>
	<?php endwhile; ?>
	</ul>
<?php endif; ?>

<?php wp_reset_query();	 // Restore global post data stomped by the_post(). ?>