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WordPress

get_tag_regex( string $tag ): string

Since
3.6.0
Source
wp-includes/functions.php:7531
Returns RegEx body to liberally match an opening HTML tag.

Description

Matches an opening HTML tag that:

  1. Is self-closing or
  2. Has no body but has a closing tag of the same name or
  3. Contains a body and a closing tag of the same name

Note: this RegEx does not balance inner tags and does not attempt to produce valid HTML

Compatibility

WordPress
since 3.6.0
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

$tagstring
An HTML tag name. Example: 'video'.

Return value

string
Tag RegEx.

Performance profile

How much work a call to get_tag_regex() 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
4–11

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 12.

Plugin surface
None

Nothing here hands control to plugin code.

Called by
0

Nothing in core calls this; the cost is only what you spend yourself.

What it touches

  • hookthird-party callbacksapply_filters()one call below get_tag_regex()

What one call costs · 2 distinct outcomes

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

WhenInstructionsCalls it makes
empty($tag)4none
!empty($tag)11tag_escape(), sprintf()

Across PHP versions

Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 12 instructions, 4–11 executed per call, 1 branch. 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.

Uses · 1

Source code

View on Trac View on GitHub 

function get_tag_regex( $tag ) {	if ( empty( $tag ) ) {		return '';	}	return sprintf( '<%1$s[^<]*(?:>[\s\S]*<\/%1$s>|\s*\/>)', tag_escape( $tag ) );}

Changelog

Introduced in 3.6.0. 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 6.8.8 tag, from src/wp-includes/functions.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.
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