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:7242
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.
Compatibility
- WordPress
- since 3.1.0
- PHP
- 7.4–8.6-dev
- 6.7.7
- 6.8.8
- 6.9.7
- 7.0.4
- 7.1.0
Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.
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 value
mixed- Scalar ID of some arbitrary member of the loop, or array of IDs of all members of loop if $_return_loop
Performance profile
How much work a call to wp_find_hierarchy_loop_tortoise_hare() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.
- Cost class
- Light
- Scaling
- Scales with input
- Instructions
- 12–52
- Plugin surface
- None
- Called by
- 1
Touches nothing outside its own arguments.
The body loops, so the work grows with what you pass in.
Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 67.
Nothing here hands control to plugin code.
1 place in core call this, so the cost is paid more often than your own code shows.
What one call costs · 3 distinct outcomes
One number would be a lie: the work depends on which branch runs. These are every distinct cost wp_find_hierarchy_loop_tortoise_hare() can have, taken from its control-flow graph on PHP 8.5.
| When | Instructions | Calls it makes |
|---|---|---|
| always | 12–32 | none |
$start && $override | 26–42 | array_merge() |
$start && $override | 40–52 | array_merge(), array_merge() |
Across PHP versions
| PHP | Compiled | Executed | Branches | Notes |
|---|---|---|---|---|
| 8.6-dev | 64 | 12–50 | 10 | 3 fewer instructions than PHP 8.5 |
| 8.5 | 67 | 12–52 | 10 | |
| 8.4 | 67 | 12–52 | 10 | |
| 8.3 | 67 | 12–52 | 10 | |
| 8.2 | 67 | 12–52 | 10 | |
| 8.1 | 67 | 12–52 | 10 | 3 more instructions than PHP 7.4 |
| 7.4 | 64 | 12–50 | 10 |
An instruction is not a fixed amount of time, so a matching count is not necessarily the same speed; what it rules out is a difference in the work itself.
Used by · 1
- wp_find_hierarchy_loop()Finds hierarchy loops using a callback function that maps object IDs to parent IDs.
Source code
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 = $override[ $hare ] ?? call_user_func_array( $callback, array_merge( array( $hare ), $callback_args ) ) ) && ( $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 = $override[ $tortoise ] ?? call_user_func_array( $callback, array_merge( array( $tortoise ), $callback_args ) ); } return false;}Changelog
Introduced in 3.1.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
About this page
- Parsed data
- Generated from the wordpress-develop 7.1.0 tag, from
src/wp-includes/functions.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it. - Corrections
- Something wrong on this page? Report it and it gets fixed in the next regeneration.