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WordPress

Walker::start_lvl( string $output, int $depth = 0, array $args = array() )

Since
2.1.0
Source
wp-includes/class-wp-walker.php:63
Starts the list before the elements are added.

Description

The $args parameter holds additional values that may be used with the child class methods. This method is called at the start of the output list.

Compatibility

WordPress
since 2.1.0
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

$outputstring
Used to append additional content (passed by reference).
$depthintoptional
Depth of the item.Default: 0
$argsarrayoptional
An array of additional arguments.Default: array()

Performance profile

How much work a call to Walker::start_lvl() 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
Trivial

Touches nothing outside its own arguments.

Scaling
Constant

No loop in the body: the same number of instructions runs whatever you pass in.

Instructions
4

Executed per call on PHP 8.5. The body compiles to 4.

Plugin surface
None

Nothing here hands control to plugin code.

Called by
1

1 place in core call this, so the cost is paid more often than your own code shows.

What one call costs · 1 distinct outcome

One number would be a lie: the work depends on which branch runs. These are every distinct cost Walker::start_lvl() can have, taken from its control-flow graph on PHP 8.5.

WhenInstructionsCalls it makes
always4none

Across PHP versions

Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 4 instructions, 4 executed per call, 0 branches. The work does not change between versions.

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

Source code

View on Trac View on GitHub 

	public function start_lvl( &$output, $depth = 0, $args = array() ) {}

Changelog

Introduced in 2.1.0. Unchanged from 6.7.7 through 7.1.0.

  1. 6.7.7
  2. 6.8.8
  3. 6.9.7
  4. 7.0.4
  5. 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/class-wp-walker.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.
Corrections
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