Populate Post Names for Dropdown field when using WP Job Manager Search and Filtering

functions.php

<?php

function smyles_populate_post_titles( $section_data, $section_id, $section ) {

	if ( ! isset( $section_data['fields'] ) || ! is_array( $section_data['fields'] ) ) {
		return $section_data;
	}

	foreach ( $section_data['fields'] as $field_id => $field ) {
		if ( $field['search_source'] == 'job_title' ) {

			// Check for a cached version first
			$cached = get_transient( 'smyles_cached_job_titles' );
			if ( false !== $cached ) {
				$section_data['fields'][ $field_id ]['data_source_options'] = $cached;
				continue;
			}

			$args = array(
				'posts_per_page' => - 1,
				'post_type'      => 'job_listing',
				'post_status'    => 'publish',
			);

			$posts             = get_posts( $args );
			$post_names        = wp_list_pluck( $posts, 'post_title' );
			$unique_post_names = array_unique( $post_names );

			$data_source_options = array();
			foreach ( $unique_post_names as $post_name ) {
				$data_source_options[] = array(
					'label' => $post_name,
					'value' => $post_name
				);
			}

			// Cache the result
			set_transient( 'smyles_cached_job_titles', $data_source_options, HOUR_IN_SECONDS );

			$section_data['fields'][ $field_id ]['data_source_options'] = $data_source_options;
		}
	}

	return $section_data;
}

add_filter( 'search_and_filtering_sections_get_section', 'smyles_populate_post_titles', 10, 3 );

// Clear the cache when a job_listing post is updated, created, or deleted
function smyles_clear_job_titles_cache( $post_id ) {

	// If this is just a revision, don't clear the cache
	if ( wp_is_post_revision( $post_id ) ) {
		return;
	}

	// Check the post type
	$post_type = get_post_type( $post_id );
	if ( 'job_listing' === $post_type ) {
		delete_transient( 'smyles_cached_job_titles' );
	}
}

add_action( 'save_post', 'smyles_clear_job_titles_cache' );
add_action( 'deleted_post', 'smyles_clear_job_titles_cache' );
add_action( 'trashed_post', 'smyles_clear_job_titles_cache' );
add_action( 'untrashed_post', 'smyles_clear_job_titles_cache' );