set_transient( string $transient, mixed $value, int $expiration )

Sets/updates the value of a transient.


Description Description

You do not need to serialize values. If the value needs to be serialized, then it will be serialized before it is set.


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Parameters Parameters

$transient

(string) (Required) Transient name. Expected to not be SQL-escaped. Must be 172 characters or fewer in length.

$value

(mixed) (Required) Transient value. Must be serializable if non-scalar. Expected to not be SQL-escaped.

$expiration

(int) (Optional) Time until expiration in seconds. Default 0 (no expiration).


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Return Return

(bool) True if the value was set, false otherwise.


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More Information More Information

For parameter $transient, if memcached is not enabled the name should be 172 characters or less in length as WordPress will prefix your name with “_transient_” or “_transient_timeout_” in the options table (depending on whether it expires or not). Longer key names will silently fail. See Trac #15058.

If a transient exists, this function will update the transient’s expiration time.

NB: transients that never expire are autoloaded, whereas transients with an expiration time are not autoloaded. Consider this when adding transients that may not be needed on every page, and thus do not need to be autoloaded, impacting page performance.

WordPress provides some constants for specifying time in seconds. Instead of multiplying out integers, see Transients_API#Using_Time_Constants.

Transient key names are limited to 191 characters due to the database schema in the wp_options table ( option_name: varchar(191) ).

In WordPress versions previous to 4.4, the length limitation was 45 in set_transient (now 172) and 64 in the database (now 191).


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Source Source

File: wp-includes/option.php

function set_transient( $transient, $value, $expiration = 0 ) {

	$expiration = (int) $expiration;

	/**
	 * Filters a specific transient before its value is set.
	 *
	 * The dynamic portion of the hook name, `$transient`, refers to the transient name.
	 *
	 * @since 3.0.0
	 * @since 4.2.0 The `$expiration` parameter was added.
	 * @since 4.4.0 The `$transient` parameter was added.
	 *
	 * @param mixed  $value      New value of transient.
	 * @param int    $expiration Time until expiration in seconds.
	 * @param string $transient  Transient name.
	 */
	$value = apply_filters( "pre_set_transient_{$transient}", $value, $expiration, $transient );

	/**
	 * Filters the expiration for a transient before its value is set.
	 *
	 * The dynamic portion of the hook name, `$transient`, refers to the transient name.
	 *
	 * @since 4.4.0
	 *
	 * @param int    $expiration Time until expiration in seconds. Use 0 for no expiration.
	 * @param mixed  $value      New value of transient.
	 * @param string $transient  Transient name.
	 */
	$expiration = apply_filters( "expiration_of_transient_{$transient}", $expiration, $value, $transient );

	if ( wp_using_ext_object_cache() ) {
		$result = wp_cache_set( $transient, $value, 'transient', $expiration );
	} else {
		$transient_timeout = '_transient_timeout_' . $transient;
		$transient_option  = '_transient_' . $transient;

		if ( false === get_option( $transient_option ) ) {
			$autoload = 'yes';
			if ( $expiration ) {
				$autoload = 'no';
				add_option( $transient_timeout, time() + $expiration, '', 'no' );
			}
			$result = add_option( $transient_option, $value, '', $autoload );
		} else {
			// If expiration is requested, but the transient has no timeout option,
			// delete, then re-create transient rather than update.
			$update = true;

			if ( $expiration ) {
				if ( false === get_option( $transient_timeout ) ) {
					delete_option( $transient_option );
					add_option( $transient_timeout, time() + $expiration, '', 'no' );
					$result = add_option( $transient_option, $value, '', 'no' );
					$update = false;
				} else {
					update_option( $transient_timeout, time() + $expiration );
				}
			}

			if ( $update ) {
				$result = update_option( $transient_option, $value );
			}
		}
	}

	if ( $result ) {

		/**
		 * Fires after the value for a specific transient has been set.
		 *
		 * The dynamic portion of the hook name, `$transient`, refers to the transient name.
		 *
		 * @since 3.0.0
		 * @since 3.6.0 The `$value` and `$expiration` parameters were added.
		 * @since 4.4.0 The `$transient` parameter was added.
		 *
		 * @param mixed  $value      Transient value.
		 * @param int    $expiration Time until expiration in seconds.
		 * @param string $transient  The name of the transient.
		 */
		do_action( "set_transient_{$transient}", $value, $expiration, $transient );

		/**
		 * Fires after the value for a transient has been set.
		 *
		 * @since 3.0.0
		 * @since 3.6.0 The `$value` and `$expiration` parameters were added.
		 *
		 * @param string $transient  The name of the transient.
		 * @param mixed  $value      Transient value.
		 * @param int    $expiration Time until expiration in seconds.
		 */
		do_action( 'setted_transient', $transient, $value, $expiration );
	}

	return $result;
}


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Changelog Changelog

Changelog
Version Description
2.8.0 Introduced.

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User Contributed Notes User Contributed Notes

  1. Skip to note 1 content
    Contributed by crstauf

    Unless you’re using an external object cache, when using set_transient() to update an existing transient that has an existing expiration, not providing an expiration value will maintain the existing expiration.

    For example:

    $initial = time();
    set_transient( 'foo', 'bar', 300 );
    sleep( 10 );
    $update = time();
    set_transient( 'foo', 'barbar' );
    

    In this case, the expiration would remain as $initial + 300 (and not change to $update + 300, or never expires), because the second set_transient() call does not include an $expiration value (only the transient’s value is updated).

    Be careful though, because you may unintentionally set a transient to never expire, if the transient expired before the second call (without the $expiration parameter) is made.

  2. Skip to note 3 content
    Contributed by Nicola Mustone

    This example shows how to set a transient with the latest five blog posts. It expires after one day.
    It uses time constants to set the expiration time.

    // Set the arguments for the custom query
    $args = array(
        'post_type'      => 'post',
        'posts_per_page' => 5,
        'orderby'        => 'date',
        'order'          => 'DESC'
    );
    $latest_post = new WP_Query( $args );
    
    // Save the results in a transient named latest_5_posts
    set_transient( 'latest_5_posts', $latest_post, DAY_IN_SECONDS );
    

    To know more about how to get posts and custom post type items read the documentation of WP_Query.

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