get_transient( string $transient )

Retrieves the value of a transient.


Description Description

If the transient does not exist, does not have a value, or has expired, then the return value will be false.


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Parameters Parameters

$transient

(string) (Required) Transient name. Expected to not be SQL-escaped.


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Return Return

(mixed) Value of transient.


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More Information More Information

$transient parameter 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.

Returned value is the value of transient. If the transient does not exist, does not have a value, or has expired, then get_transient will return false. This should be checked using the identity operator ( === ) instead of the normal equality operator, because an integer value of zero (or other “empty” data) could be the data you’re wanting to store. Because of this “false” value, transients should not be used to hold plain boolean values. Put them into an array or convert them to integers instead.


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Source Source

File: wp-includes/option.php

function get_transient( $transient ) {

	/**
	 * Filters the value of an existing transient before it is retrieved.
	 *
	 * The dynamic portion of the hook name, `$transient`, refers to the transient name.
	 *
	 * Returning a truthy value from the filter will effectively short-circuit retrieval
	 * and return the passed value instead.
	 *
	 * @since 2.8.0
	 * @since 4.4.0 The `$transient` parameter was added
	 *
	 * @param mixed  $pre_transient The default value to return if the transient does not exist.
	 *                              Any value other than false will short-circuit the retrieval
	 *                              of the transient, and return that value.
	 * @param string $transient     Transient name.
	 */
	$pre = apply_filters( "pre_transient_{$transient}", false, $transient );

	if ( false !== $pre ) {
		return $pre;
	}

	if ( wp_using_ext_object_cache() ) {
		$value = wp_cache_get( $transient, 'transient' );
	} else {
		$transient_option = '_transient_' . $transient;
		if ( ! wp_installing() ) {
			// If option is not in alloptions, it is not autoloaded and thus has a timeout.
			$alloptions = wp_load_alloptions();
			if ( ! isset( $alloptions[ $transient_option ] ) ) {
				$transient_timeout = '_transient_timeout_' . $transient;
				$timeout           = get_option( $transient_timeout );
				if ( false !== $timeout && $timeout < time() ) {
					delete_option( $transient_option );
					delete_option( $transient_timeout );
					$value = false;
				}
			}
		}

		if ( ! isset( $value ) ) {
			$value = get_option( $transient_option );
		}
	}

	/**
	 * Filters an existing transient's value.
	 *
	 * The dynamic portion of the hook name, `$transient`, refers to the transient name.
	 *
	 * @since 2.8.0
	 * @since 4.4.0 The `$transient` parameter was added
	 *
	 * @param mixed  $value     Value of transient.
	 * @param string $transient Transient name.
	 */
	return apply_filters( "transient_{$transient}", $value, $transient );
}


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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 RavanH

    Useful to know: If the transient exists but has expired, the return value will not just be false. The expired transient will be deleted at the same time.

    WordPress does not delete expired transients on its own, but using get_transient() on an expired one will do so. Non-expired transients, or transients without expiration will only be deleted with delete_transient().

  2. Skip to note 2 content
    Contributed by Codex

    Example of using get_transient, set_transient and WP_Query

    // Get any existing copy of our transient data
    if ( false === ( $special_query_results = get_transient( 'special_query_results' ) ) ) {
    	// It wasn't there, so regenerate the data and save the transient
    	$special_query_results = new WP_Query( 'cat=5&order=random&tag=tech&post_meta_key=thumbnail' );
    	set_transient( 'special_query_results', $special_query_results );
    }
    
    // Use the data like you would have normally...
    
  3. Skip to note 3 content
    Contributed by Codex

    Add WP_DEBUG in the conditional statement if you always want live data during development stage

    <?php
    
    if ( WP_DEBUG or false === ( $special_query_results = get_transient( 'special_query_results' ) ) ) ) {
    	// It wasn't there, so regenerate the data and save the transient
    	$special_query_results = new WP_Query( 'cat=5&order=random&tag=tech&post_meta_key=thumbnail' );
    	set_transient( 'special_query_results', $special_query_results );
    }
    
    ?>
    
    

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