diff --git a/src/wp-includes/class-wp-theme-json.php b/src/wp-includes/class-wp-theme-json.php
index 4da9580271ff8..2704c78c7e33f 100644
--- a/src/wp-includes/class-wp-theme-json.php
+++ b/src/wp-includes/class-wp-theme-json.php
@@ -2194,13 +2194,20 @@ protected static function compute_style_properties( $styles, $settings = array()
 		}
 
 		$root_variable_duplicates = array();
+		$update_cache             = false;
+		$str_start_with_cache     = (array) wp_cache_get( 'str_start_with', 'theme_files' );
+		$str_len_root             = strlen( '--wp--style--root--' );
 
 		foreach ( $properties as $css_property => $value_path ) {
-			$value = static::get_property_value( $styles, $value_path, $theme_json );
-
-			if ( str_starts_with( $css_property, '--wp--style--root--' ) && ( static::ROOT_BLOCK_SELECTOR !== $selector || ! $use_root_padding ) ) {
+			if ( ! isset( $str_start_with_cache[ $css_property ] ) ) {
+				$str_start_with_cache[ $css_property ] = str_starts_with( $css_property, '--wp--style--root--' );
+				$update_cache                          = true;
+			}
+			if ( $str_start_with_cache[ $css_property ] && ( static::ROOT_BLOCK_SELECTOR !== $selector || ! $use_root_padding ) ) {
 				continue;
 			}
+
+			$value = static::get_property_value( $styles, $value_path, $theme_json );
 			/*
 			 * Root-level padding styles don't currently support strings with CSS shorthand values.
 			 * This may change: https://github.com/WordPress/gutenberg/issues/40132.
@@ -2209,8 +2216,8 @@ protected static function compute_style_properties( $styles, $settings = array()
 				continue;
 			}
 
-			if ( str_starts_with( $css_property, '--wp--style--root--' ) && $use_root_padding ) {
-				$root_variable_duplicates[] = substr( $css_property, strlen( '--wp--style--root--' ) );
+			if ( $str_start_with_cache[ $css_property ] && $use_root_padding ) {
+				$root_variable_duplicates[] = substr( $css_property, $str_len_root );
 			}
 
 			/*
@@ -2218,7 +2225,13 @@ protected static function compute_style_properties( $styles, $settings = array()
 			 * Skip protected properties that are explicitly set to `null`.
 			 */
 			if ( is_array( $value_path ) ) {
-				$path_string = implode( '.', $value_path );
+				$path_string = '';
+				for ( $i = 0; $i < count( $value_path ); $i++ ) {
+					if ( $i > 0 ) {
+						$path_string .= '.';
+					}
+					$path_string .= $value_path[ $i ];
+				}
 				if (
 					isset( static::PROTECTED_PROPERTIES[ $path_string ] ) &&
 					_wp_array_get( $settings, static::PROTECTED_PROPERTIES[ $path_string ], null ) === null
@@ -2233,9 +2246,7 @@ protected static function compute_style_properties( $styles, $settings = array()
 				$value             = isset( $background_styles['declarations'][ $css_property ] ) ? $background_styles['declarations'][ $css_property ] : $value;
 			}
 
-			// Skip if empty and not "0" or value represents array of longhand values.
-			$has_missing_value = empty( $value ) && ! is_numeric( $value );
-			if ( $has_missing_value || is_array( $value ) ) {
+			if ( '' === $value || is_array( $value ) ) {
 				continue;
 			}
 
@@ -2267,6 +2278,10 @@ protected static function compute_style_properties( $styles, $settings = array()
 			);
 		}
 
+		if ( $update_cache ) {
+			wp_cache_set( 'str_start_with', $str_start_with_cache, 'theme_files' );
+		}
+
 		// If a variable value is added to the root, the corresponding property should be removed.
 		foreach ( $root_variable_duplicates as $duplicate ) {
 			$discard = array_search( $duplicate, array_column( $declarations, 'name' ), true );