post_meta_transient.php

<?php
/**
 * Delete a post meta transient.
 */
function delete_post_meta_transient( $post_id, $transient, $value = null ) {
	global $_wp_using_ext_object_cache;

	$post_id = (int) $post_id;

	do_action( 'delete_post_meta_transient_' . $transient, $post_id, $transient );

	if ( $_wp_using_ext_object_cache ) {
		$result = wp_cache_delete( "{$transient}-{$post_id}", "post_meta_transient-{$post_id}" );
	} else {
		$meta_timeout = '_transient_timeout_' . $transient;
		$meta = '_transient_' . $transient;
		$result = delete_post_meta( $post_id, $meta, $value );
		if ( $result )
			delete_post_meta( $post_id, $meta_timeout, $value );
	}

	if ( $result )
		do_action( 'deleted_post_meta_transient', $transient, $post_id, $transient );
	return $result;
}

/**
 * Get the value of a post meta transient.
 */
function get_post_meta_transient( $post_id, $transient ) {
	global $_wp_using_ext_object_cache;

	$post_id = (int) $post_id;

	if (has_filter('pre_post_meta_transient_' . $transient)) {
		$pre = apply_filters( 'pre_post_meta_transient_' . $transient, $post_id, $transient );
		if ( false !== $pre )
			return $pre;
	}

	if ( $_wp_using_ext_object_cache ) {
		$value = wp_cache_get( "{$transient}-{$post_id}", "post_meta_transient-{$post_id}" );
	} else {
		$meta_timeout = '_transient_timeout_' . $transient;
		$meta = '_transient_' . $transient;
		$value = get_post_meta( $post_id, $meta, true );
		if ( $value && ! defined( 'WP_INSTALLING' ) ) {
			if ( get_post_meta( $post_id, $meta_timeout, true ) < time() ) {
				delete_post_meta_transient( $post_id, $transient );
				return false;
			}
		}
	}

	return 
		has_filter('post_meta_transient_' . $transient)
		? apply_filters( 'post_meta_transient_' . $transient, $value, $post_id )
		: $value;
}

/**
 * Set/update the value of a post meta transient.
 */
function set_post_meta_transient( $post_id, $transient, $value, $expiration = 0 ) {
	global $_wp_using_ext_object_cache;

	$post_id = (int) $post_id;

	delete_post_meta_transient( $post_id, $transient );
	if (has_filter('pre_set_post_meta_transient_' . $transient))
		$value = apply_filters( 'pre_set_post_meta_transient_' . $transient, $value, $post_id, $transient );

	if ( $_wp_using_ext_object_cache ) {
		$result = wp_cache_set( "{$transient}-{$post_id}", $value, "post_meta_transient-{$post_id}", $expiration );
	} else {
		$meta_timeout = '_transient_timeout_' . $transient;
		$meta = '_transient_' . $transient;
		if ( $expiration ) {
			add_post_meta( $post_id, $meta_timeout, time() + $expiration, true );
		}
		$result = add_post_meta( $post_id, $meta, $value, true );
	}
	if ( $result ) {
		do_action( 'set_post_meta_transient_' . $transient, $post_id, $transient );
		do_action( 'setted_post_meta_transient', $transient, $post_id, $transient );
	}
	return $result;
}