Compiles styles from stores or collections of CSS rules into a stylesheet.

Source: wp-includes/style-engine/class-wp-style-engine-processor.php
Since: 6.1.0

Properties

Methods

add_store()

Adds a store to the processor.

public function add_store( WP_Style_Engine_CSS_Rules_Store $store ): WP_Style_Engine_Processor

Parameters

Returns

$this for method chaining.

Notes

Triggers _doing_it_wrong() if $store is not a WP_Style_Engine_CSS_Rules_Store instance.

Example

$processor = new WP_Style_Engine_Processor();
$store = WP_Style_Engine_CSS_Rules_Store::get_store( 'my-context' );
$processor->add_store( $store );

add_rules()

Adds rules to be processed.

public function add_rules( 
    WP_Style_Engine_CSS_Rule|WP_Style_Engine_CSS_Rule[] $css_rules 
): WP_Style_Engine_Processor

Since: 6.1.0
Since: 6.6.0 Added support for rules_group

Parameters

Returns

$this for method chaining.

Behavior

• Rules with the same selector are merged (declarations combined)
• Rules with a rules_group are keyed by "$rules_group $selector" to maintain separation
• Existing rules are updated with new declarations rather than duplicated

Example

$processor = new WP_Style_Engine_Processor();

// Add single rule
$processor->add_rules( new WP_Style_Engine_CSS_Rule( '.a', array( 'color' => 'red' ) ) );

// Add multiple rules
$processor->add_rules( array(
    new WP_Style_Engine_CSS_Rule( '.b', array( 'color' => 'blue' ) ),
    new WP_Style_Engine_CSS_Rule( '.c', array( 'color' => 'green' ) ),
) );

// Merge declarations into existing selector
$processor->add_rules( new WP_Style_Engine_CSS_Rule( '.a', array( 'font-size' => '16px' ) ) );
// .a now has both color:red and font-size:16px

get_css()

Gets the compiled CSS string.

public function get_css( array $options = array() ): string

Since: 6.1.0
Since: 6.4.0 Optimization no longer the default

Parameters

Options

Returns

Compiled CSS string.

Process

1. Collects rules from all added stores
2. If optimize is true, combines selectors with identical declarations
3. Compiles each rule to CSS
4. Concatenates all rules

Example

$processor = new WP_Style_Engine_Processor();

$processor->add_rules( array(
    new WP_Style_Engine_CSS_Rule( '.a', array( 'color' => 'red' ) ),
    new WP_Style_Engine_CSS_Rule( '.b', array( 'color' => 'red' ) ),
    new WP_Style_Engine_CSS_Rule( '.c', array( 'font-size' => '16px' ) ),
) );

// Without optimization
echo $processor->get_css();
// Output: '.a{color:red}.b{color:red}.c{font-size:16px}'

// With optimization (combine .a and .b)
echo $processor->get_css( array( 'optimize' => true ) );
// Output: '.a,.b{color:red}.c{font-size:16px}'

// Prettified
echo $processor->get_css( array( 'prettify' => true ) );
// Output:
// .a {
// 	color: red;
// }
// .b {
// 	color: red;
// }
// .c {
// 	font-size: 16px;
// }

Private Methods

combine_rules_selectors()

Combines selectors from rules when they have identical declarations.

private function combine_rules_selectors(): void

Behavior

1. Serializes each rule’s declarations to JSON for comparison
2. Finds rules with identical declaration sets
3. Merges their selectors (comma-separated)
4. Removes duplicate rules, keeping combined version

Example Effect

Before:

.a { color: red; }
.b { color: red; }
.c { color: blue; }

After optimization:

.a, .b { color: red; }
.c { color: blue; }