wp_find_hierarchy_loop_tortoise_hare( callable $callback, int $start, array $override = array(), array $callback_args = array(), bool $_return_loop = false ): mixed
- Since
- 3.1.0
- Source
wp-includes/functions.php:7114
Uses the "The Tortoise and the Hare" algorithm to detect loops.
Description
For every step of the algorithm, the hare takes two steps and the tortoise one.If the hare ever laps the tortoise, there must be a loop.
Parameters
$callbackcallable- Function that accepts ( ID, callback_arg, ... ) and outputs parent_ID.
$startint- The ID to start the loop check at.
$overridearrayoptional- An array of ( ID => parent_ID, ... ) to use instead of $callback. Default empty array.Default:
array() $callback_argsarrayoptional- Additional arguments to send to $callback. Default empty array.Default:
array() $_return_loopbooloptional- Return loop members or just detect presence of loop? Only set to true if you already know the given $start is part of a loop (otherwise the returned array might include branches). Default false.Default:
false
Return
mixed- Scalar ID of some arbitrary member of the loop, or array of IDs of all members of loop if $_return_loop
Used by · 1
- wp_find_hierarchy_loop()Finds hierarchy loops using a callback function that maps object IDs to parent IDs.
Source
function wp_find_hierarchy_loop_tortoise_hare( $callback, $start, $override = array(), $callback_args = array(), $_return_loop = false ) { $tortoise = $start; $hare = $start; $evanescent_hare = $start; $return = array(); // Set evanescent_hare to one past hare. Increment hare two steps. while ( $tortoise && ( $evanescent_hare = isset( $override[ $hare ] ) ? $override[ $hare ] : call_user_func_array( $callback, array_merge( array( $hare ), $callback_args ) ) ) && ( $hare = isset( $override[ $evanescent_hare ] ) ? $override[ $evanescent_hare ] : call_user_func_array( $callback, array_merge( array( $evanescent_hare ), $callback_args ) ) ) ) { if ( $_return_loop ) { $return[ $tortoise ] = true; $return[ $evanescent_hare ] = true; $return[ $hare ] = true; } // Tortoise got lapped - must be a loop. if ( $tortoise === $evanescent_hare || $tortoise === $hare ) { return $_return_loop ? $return : $tortoise; } // Increment tortoise by one step. $tortoise = isset( $override[ $tortoise ] ) ? $override[ $tortoise ] : call_user_func_array( $callback, array_merge( array( $tortoise ), $callback_args ) ); } return false;}History
Introduced in 3.1.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
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