Better ways to retrieve custom fields get_post_meta()

get-post-meta.php

<?php 

/**
 * Retrieve a single value of a custom field
 *
 * A wrapper for get_post_meta to make it so the $post_id is not required.
 *
 * @param unknown $key  string - the custom field key
 * @param unknown $p_id int (optional) - the post ID for post to retrieve the value from, defaults to current post
 */
function theme_slug_get_field( $key, $p_id=null ) {
	// Populate $p_id if empty with the current post
	if ( empty( $p_id ) ) {
		$p_id = get_the_ID();
	}

	return get_post_meta( $p_id, $key, true );
}

/**
 * Print out a single value of a custom field
 *
 * @param unknown $key  string - the custom field key
 * @param unknown $p_id int (optional) - the post ID for post to retrieve the value from, defaults to current post
 */
function theme_slug_the_field( $key, $p_id=null, $esc_method='attr' ) {
	$value = theme_slug_get_field( $key, $p_id );

	if ( $esc_method == 'text' ) {
		echo esc_html( $value );
	} elseif ( $esc_method == 'url' ) {
		echo esc_url( $value );
	} elseif ( $esc_method == 'html' ) {
		echo wp_kses_post( $value );
	} else {
		echo esc_attr( $value );
	}
}

/**
 * Retrieve multiple values of a custom field
 *
 * @param unknown $key  string - the custom field key
 * @param unknown $p_id int (optional) - the post ID for post to retrieve the value from, defaults to current post
 */
function theme_slug_get_multiple_field( $key, $p_id=null ) {
	// Populate $p_id if empty with the current post
	if ( empty( $p_id ) ) {
		$p_id = get_the_ID();
	}

	return get_post_meta( $p_id, $key, false );
}