wppaste
WordPress

WP_Theme_JSON::split_selector_list( string $selector ): string[]

Since
7.1.0
Source
wp-includes/class-wp-theme-json.php:1612
Splits a selector list into separate selectors.

Description

While selectors are joined by commas, not all commas separate top-level selectors.
This method only separates top-level selectors, so some commas may appear inside strings, nested selectors, and comments. Leading and trailing CSS whitespace is trimmed from the returned list items.

Non-selector content, such as comments, are retained in the list in the same item as the selector content they follow.

Example:

array( '.wp-block' ) === self::split_selector_list( '.wp-block' );
array( '.one', '.two' ) === self::split_selector_list( '.one, .two' );

// Nested selector lists are retained within their containing selector.
array( ':is(.a, .b)', 'c' ) === self::split_selector_list( ':is(.a, .b), .c' );

// Commas within strings do not separate selectors.
$selectors = self::split_selector_list( '[data-label="Save, continue"],.fallback' );
$selectors === array( '[data-label="Save, continue"]', '.fallback' )

array( 'lang(zh, "*-hant")', '.foo' ) === self::split_selector_list( 'lang(zh, "*-hant"), .foo' );

// Identifiers may contain escaped commas.
array( '.foo\,bar', '.baz' ) === self::split_selector_list( '.foo\,bar,.baz' );

// Comments stay with the selector they follow.
array( '.a /* a, the first *\/', '.b' ) === self::split_selector_list( '.a /* a, the first *\/,.b' );

Compatibility

WordPress
since 7.1.0
PHP
7.4–8.6-dev
  • 6.7.7
  • 6.8.8
  • 6.9.7
  • 7.0.4
  • 7.1.0

Present in 1 of the 5 tracked releases, added in 7.1.0, and compiles on PHP 7.4 through 8.6-dev.

Parameters

$selectorstring
CSS selector list as a string, e.g. '.wp-block .wp-block-paragraph'.

Return value

string[]
List of trimmed selectors parsed from input list.

Performance profile

How much work a call to WP_Theme_JSON::split_selector_list() 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

Touches nothing outside its own arguments.

Scaling
Scales with input

The body loops, so the work grows with what you pass in.

Instructions
6–26

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 144.

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 one call costs · 2 distinct outcomes

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

WhenInstructionsCalls it makes
always6–18none
$selector && $at && $selector_length22–26strcspn()

Across PHP versions

PHPCompiledExecutedBranchesNotes
8.6-dev1446–2625
8.51446–2625
8.41446–262524 fewer instructions than PHP 8.3
8.316812–3525
8.216812–3525
8.116812–35252 fewer instructions than PHP 7.4
7.417012–3525

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

  • str_contains()Polyfill for `str_contains()` function added in PHP 8.0.

Source code

View on Trac View on GitHub 

	protected static function split_selector_list( $selector ): array {		if ( ! str_contains( $selector, ',' ) ) {			// See note on trimming CSS whitespace in main loop.			return array( trim( $selector, " \t\n" ) );		} 		$selectors         = array();		$selector_length   = strlen( $selector );		$parentheses_depth = 0;		$at                = 0;		$was_at            = 0; 		while ( $at < $selector_length ) {			$next_at = $at + strcspn( $selector, '/,\'"()<-\\', $at );			if ( $next_at >= $selector_length ) {				break;			} 			$next_cp = $selector[ $next_at ]; 			// Escaped syntax characters do not act as delimiters.			if ( '\\' === $next_cp ) {				$at = min( $next_at + 2, $selector_length );				continue;			} 			/*			 * Start of a parenthesized expression, which maintains a stack of parentheses.			 * For the sake of this function, no selector list will be split inside parentheses.			 * Therefore it’s possible to jump ahead until this list completes.			 */			if ( '(' === $next_cp || ')' === $next_cp ) {				$parentheses_depth += '(' === $next_cp ? 1 : -1;				$at                 = $next_at + 1;				continue;			} 			// Start of a string, which will be incorporated into the selector in which it’s found.			if ( "'" === $next_cp || '"' === $next_cp ) {				$end_of_string = $next_at + 1;				while ( $end_of_string < $selector_length ) {					$end_of_string += strcspn( $selector, "{$next_cp}\\", $end_of_string );					if ( $end_of_string >= $selector_length ) {						break;					} 					$end_cp = $selector[ $end_of_string ]; 					// Skip escaped characters.					if ( '\\' === $end_cp ) {						$end_of_string = $end_of_string + 2;						continue;					} 					if ( $next_cp === $end_cp ) {						++$end_of_string;						break;					} 					++$end_of_string;				} 				$at = $end_of_string;				continue;			} 			// Start of a comment, which will be incorporated into the selector in which it’s found.			if ( '/' === $next_cp && ( $next_at + 1 ) < $selector_length && '*' === $selector[ $next_at + 1 ] ) {				$comment_end_at = strpos( $selector, '*/', $next_at + 1 );				$is_terminated  = false !== $comment_end_at;				$after_comment  = $is_terminated ? $comment_end_at + 2 : strlen( $selector );				$at             = $after_comment;				continue;			} 			// Start of a CDO or CDC, which will be incorporated into the selector in which it’s found.			if (				( '<' === $next_cp && 0 === substr_compare( $selector, '<!--', $next_at, 4 ) ) ||				( '-' === $next_cp && 0 === substr_compare( $selector, '-->', $next_at, 3 ) )			) {

Changelog

Introduced in 7.1.0.

Signature, return type and hooks compared across 1 parsed release.

About this page

Parsed data
Generated from the wordpress-develop 7.1.0 tag, from src/wp-includes/class-wp-theme-json.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.