wp-includes/functions.wp-styles.php:87Adds extra CSS styles to a registered stylesheet.
$handlestring$datastringboolfunction wp_add_inline_style( $handle, $data ) { _wp_scripts_maybe_doing_it_wrong( __FUNCTION__, $handle ); if ( false !== stripos( $data, '</style>' ) ) { _doing_it_wrong( __FUNCTION__, sprintf( /* translators: 1: <style>, 2: wp_add_inline_style() */ __( 'Do not pass %1$s tags to %2$s.' ), '<code><style></code>', '<code>wp_add_inline_style()</code>' ), '3.7.0' ); $data = trim( preg_replace( '#<style[^>]*>(.*)</style>#is', '$1', $data ) ); } return wp_styles()->add_inline_style( $handle, $data );}Introduced in 3.3.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/functions.wp-styles.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.