Use the Style Engine when input already follows WordPress's structured block\nstyle shape or when several selector/declaration pairs must become one\nstylesheet. It reduces hand-built CSS and preserves preset-token conventions,\nbut it is not a general CSS parser and it does not make arbitrary selectors or\nat-rules trustworthy.
\n| Need | \nFunction | \n
|---|---|
| Convert one block/theme style object to declarations, CSS, and class names | \nwp_style_engine_get_styles() | \n
| Compile multiple selector/declaration rules | \nwp_style_engine_get_stylesheet_from_css_rules() | \n
| Compile rules accumulated under a request-local context | \nwp_style_engine_get_stylesheet_from_context() | \n
Core explicitly marks WP_Style_Engine itself as internal and directs\nextenders to wp_style_engine_get_styles(). Do not call its parsing,\ncompilation, or store methods directly merely because they are public PHP\nmethods.
$generated = wp_style_engine_get_styles(\n\tarray(\n\t\t'color' => array( 'text' => 'var:preset|color|contrast' ),\n\t\t'dimensions' => array( 'minWidth' => '18rem' ),\n\t),\n\tarray(\n\t\t'selector' => '.acme-card',\n\t\t'context' => 'acme-card',\n\t)\n);\n\n$class_names = $generated['classnames'] ?? '';\n$css = $generated['css'] ?? '';\nThe return keys are conditional; do not assume css, declarations, or\nclassnames always exists. Preset strings can become CSS variables and class\nnames. When outputting a dynamic block, combine plugin-owned classes with\nget_block_wrapper_attributes() and escape any additional attribute values.
WordPress 7.1 adds Style Engine support relevant to\nbackground.gradient and dimensions.minWidth. The registered block and\ntheme settings still determine whether editor controls are offered; generating\nCSS does not grant support to a block by itself.
$css = wp_style_engine_get_stylesheet_from_css_rules(\n\tarray(\n\t\tarray(\n\t\t\t'selector' => '.acme-card',\n\t\t\t'declarations' => array(\n\t\t\t\t'color' => '#222',\n\t\t\t\t'padding' => '1rem',\n\t\t\t),\n\t\t),\n\t\tarray(\n\t\t\t'rules_group' => '@media (max-width: 48rem)',\n\t\t\t'selector' => '.acme-card',\n\t\t\t'declarations' => array( 'padding' => '0.75rem' ),\n\t\t),\n\t),\n\tarray(\n\t\t'optimize' => true,\n\t\t'prettify' => defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG,\n\t)\n);\n\nif ( '' !== $css ) {\n\twp_add_inline_style( 'acme-card', $css );\n}\nRules without a non-empty selector or declarations are skipped. rules_group\nsupports parent selectors and nested at-rules, but both it and selector are\nstructural input owned by the caller. Never interpolate request data, database\nlabels, post content, or remote values into either field.
Declaration properties are normalized and values pass through WordPress safe\nCSS filtering during compilation. That is not enough to make attacker-chosen\nrule structure safe.
\nIn WordPress 7.1, a stylesheet rule may receive a\nWP_Style_Engine_CSS_Declarations object and retain per-declaration options.\nThis is the supported way to request !important from this API:
$declarations = new WP_Style_Engine_CSS_Declarations();\n$declarations->add_declaration(\n\t'display',\n\t'none',\n\tarray( 'important' => true )\n);\n\n$css = wp_style_engine_get_stylesheet_from_css_rules(\n\tarray(\n\t\tarray(\n\t\t\t'selector' => '.acme-is-hidden',\n\t\t\t'declarations' => $declarations,\n\t\t),\n\t)\n);\nUse !important only for a measured cascade requirement, not as a default.\nThe option is appended only when the filtered result is one valid declaration.\nFeature-detect the WordPress version before passing the object when supporting\n7.0 or older; prior versions documented declarations as arrays.
Passing the same non-empty context and selectors stores rules in the Style\nEngine registry for the current PHP request. Later,\nwp_style_engine_get_stylesheet_from_context( 'acme-card' ) compiles that\nstore. It does not save rules to the database or carry them into another\nrequest.
Use a namespaced context, emit the result once, and avoid mixing unrelated\nfrontend/admin/editor policies into the same store. A context is an aggregation\nkey, not a CSS scoping boundary or an authorization mechanism.
\n!important.Read references/output-and-testing.md for context and security probes.
wp-block-registration-and-assets for block metadata and wrapper output.block-theme-global-styles for WordPress 7.1 theme.json responsive states.wp-block-editor-iframe-compatibility for editor asset placement.wp-plugin-assets-loading for registering and printing the target stylesheet.wp-includes/style-engine.php.wp-includes/style-engine/class-wp-style-engine.php.wp-includes/style-engine/class-wp-style-engine-css-declarations.php.