diff --git a/lib/block-supports/duotone.php b/lib/block-supports/duotone.php
index d12582b6a768cc..5cb7fb7cfc5ac6 100644
--- a/lib/block-supports/duotone.php
+++ b/lib/block-supports/duotone.php
@@ -16,14 +16,14 @@
  * @return float      Value in the range [0,1].
  */
 function gutenberg_tinycolor_bound01( $n, $max ) {
-	if ( 'string' === gettype( $n ) && false !== strpos( $n, '.' ) && 1 === (float) $n ) {
+	if ( 'string' === gettype( $n ) && str_contains( $n, '.' ) && 1 === (float) $n ) {
 		$n = '100%';
 	}
 
 	$n = min( $max, max( 0, (float) $n ) );
 
 	// Automatically convert percentage into number.
-	if ( 'string' === gettype( $n ) && false !== strpos( $n, '%' ) ) {
+	if ( 'string' === gettype( $n ) && str_contains( $n, '%' ) ) {
 		$n = (int) ( $n * $max ) / 100;
 	}
 
diff --git a/lib/block-supports/elements.php b/lib/block-supports/elements.php
index 47c12dc9dcbb3e..0b6e31db3d66d3 100644
--- a/lib/block-supports/elements.php
+++ b/lib/block-supports/elements.php
@@ -58,7 +58,7 @@ function gutenberg_render_elements_support( $block_content, $block ) {
 	$first_element = $html_element_matches[0][0];
 	// If the first HTML element has a class attribute just add the new class
 	// as we do on layout and duotone.
-	if ( strpos( $first_element, 'class="' ) !== false ) {
+	if ( str_contains( $first_element, 'class="' ) ) {
 		$content = preg_replace(
 			'/' . preg_quote( 'class="', '/' ) . '/',
 			'class="' . $class_name . ' ',
diff --git a/lib/block-supports/layout.php b/lib/block-supports/layout.php
index 990e78996e045e..7047b4a3a28f0f 100644
--- a/lib/block-supports/layout.php
+++ b/lib/block-supports/layout.php
@@ -106,7 +106,7 @@ function gutenberg_get_layout_style( $selector, $layout, $has_block_gap_support
 			}
 			if ( $gap_value && ! $should_skip_gap_serialization ) {
 				// Get spacing CSS variable from preset value if provided.
-				if ( is_string( $gap_value ) && strpos( $gap_value, 'var:preset|spacing|' ) !== false ) {
+				if ( is_string( $gap_value ) && str_contains( $gap_value, 'var:preset|spacing|' ) ) {
 					$index_to_splice = strrpos( $gap_value, '|' ) + 1;
 					$slug            = _wp_to_kebab_case( substr( $gap_value, $index_to_splice ) );
 					$gap_value       = "var(--wp--preset--spacing--$slug)";
@@ -164,7 +164,7 @@ function gutenberg_get_layout_style( $selector, $layout, $has_block_gap_support
 			foreach ( $gap_sides as $gap_side ) {
 				$process_value = is_string( $gap_value ) ? $gap_value : _wp_array_get( $gap_value, array( $gap_side ), $fallback_gap_value );
 				// Get spacing CSS variable from preset value if provided.
-				if ( is_string( $process_value ) && strpos( $process_value, 'var:preset|spacing|' ) !== false ) {
+				if ( is_string( $process_value ) && str_contains( $process_value, 'var:preset|spacing|' ) ) {
 					$index_to_splice = strrpos( $process_value, '|' ) + 1;
 					$slug            = _wp_to_kebab_case( substr( $process_value, $index_to_splice ) );
 					$process_value   = "var(--wp--preset--spacing--$slug)";
diff --git a/lib/block-supports/typography.php b/lib/block-supports/typography.php
index 8cfeda2b0641b5..6cfae5b8cf07eb 100644
--- a/lib/block-supports/typography.php
+++ b/lib/block-supports/typography.php
@@ -171,7 +171,7 @@ function gutenberg_apply_typography_support( $block_type, $block_attributes ) {
  */
 function gutenberg_typography_get_preset_inline_style_value( $style_value, $css_property ) {
 	// If the style value is not a preset CSS variable go no further.
-	if ( empty( $style_value ) || strpos( $style_value, "var:preset|{$css_property}|" ) === false ) {
+	if ( empty( $style_value ) || ! str_contains( $style_value, "var:preset|{$css_property}|" ) ) {
 		return $style_value;
 	}
 
@@ -209,7 +209,7 @@ function gutenberg_typography_get_css_variable_inline_style( $attributes, $featu
 	}
 
 	// If we don't have a preset CSS variable, we'll assume it's a regular CSS value.
-	if ( strpos( $style_value, "var:preset|{$css_property}|" ) === false ) {
+	if ( ! str_contains( $style_value, "var:preset|{$css_property}|" ) ) {
 		return sprintf( '%s:%s;', $css_property, $style_value );
 	}
 
diff --git a/lib/compat/wordpress-6.1/get-global-styles-and-settings.php b/lib/compat/wordpress-6.1/get-global-styles-and-settings.php
index 5dd950c627a641..32fde3442577b8 100644
--- a/lib/compat/wordpress-6.1/get-global-styles-and-settings.php
+++ b/lib/compat/wordpress-6.1/get-global-styles-and-settings.php
@@ -33,7 +33,7 @@ function wp_add_global_styles_for_blocks() {
 				array_filter(
 					$metadata['path'],
 					function ( $item ) {
-						if ( strpos( $item, 'core/' ) !== false ) {
+						if ( str_contains( $item, 'core/' ) ) {
 							return true;
 						}
 						return false;
diff --git a/lib/experimental/class-wp-webfonts-provider-local.php b/lib/experimental/class-wp-webfonts-provider-local.php
index a8c4fa7968961f..9af27fa7c436a7 100644
--- a/lib/experimental/class-wp-webfonts-provider-local.php
+++ b/lib/experimental/class-wp-webfonts-provider-local.php
@@ -185,9 +185,9 @@ private function build_font_face_css( array $webfont ) {
 
 		// Wrap font-family in quotes if it contains spaces.
 		if (
-			false !== strpos( $webfont['font-family'], ' ' ) &&
-			false === strpos( $webfont['font-family'], '"' ) &&
-			false === strpos( $webfont['font-family'], "'" )
+			str_contains( $webfont['font-family'], ' ' ) &&
+			! str_contains( $webfont['font-family'], '"' ) &&
+			! str_contains( $webfont['font-family'], "'" )
 		) {
 			$webfont['font-family'] = '"' . $webfont['font-family'] . '"';
 		}
diff --git a/packages/block-library/src/calendar/index.php b/packages/block-library/src/calendar/index.php
index 9225a6dceb4887..8f6226e943480c 100644
--- a/packages/block-library/src/calendar/index.php
+++ b/packages/block-library/src/calendar/index.php
@@ -30,8 +30,8 @@ function render_block_core_calendar( $attributes ) {
 	if ( isset( $attributes['month'] ) && isset( $attributes['year'] ) ) {
 		$permalink_structure = get_option( 'permalink_structure' );
 		if (
-			strpos( $permalink_structure, '%monthnum%' ) !== false &&
-			strpos( $permalink_structure, '%year%' ) !== false
+			str_contains( $permalink_structure, '%monthnum%' ) &&
+			str_contains( $permalink_structure, '%year%' )
 		) {
 			// phpcs:ignore WordPress.WP.GlobalVariablesOverride.OverrideProhibited
 			$monthnum = $attributes['month'];
diff --git a/packages/block-library/src/image/index.php b/packages/block-library/src/image/index.php
index 70fa3a0a303793..9a9f175556e814 100644
--- a/packages/block-library/src/image/index.php
+++ b/packages/block-library/src/image/index.php
@@ -20,7 +20,7 @@ function render_block_core_image( $attributes, $content ) {
 		// which now wraps Image Blocks within innerBlocks.
 		// The data-id attribute is added in a core/gallery `render_block_data` hook.
 		$data_id_attribute = 'data-id="' . esc_attr( $attributes['data-id'] ) . '"';
-		if ( false === strpos( $content, $data_id_attribute ) ) {
+		if ( ! str_contains( $content, $data_id_attribute ) ) {
 			$content = str_replace( '<img', '<img ' . $data_id_attribute . ' ', $content );
 		}
 	}
diff --git a/packages/block-library/src/search/index.php b/packages/block-library/src/search/index.php
index 1ba3229b98a645..d056da16d958a5 100644
--- a/packages/block-library/src/search/index.php
+++ b/packages/block-library/src/search/index.php
@@ -217,7 +217,7 @@ function apply_block_core_search_border_style( $attributes, $property, $side, &$
 	}
 
 	if ( 'color' === $property && $side ) {
-		$has_color_preset = strpos( $value, 'var:preset|color|' ) !== false;
+		$has_color_preset = str_contains( $value, 'var:preset|color|' );
 		if ( $has_color_preset ) {
 			$named_color_value = substr( $value, strrpos( $value, '|' ) + 1 );
 			$value             = sprintf( 'var(--wp--preset--color--%s)', $named_color_value );
diff --git a/packages/style-engine/class-wp-style-engine.php b/packages/style-engine/class-wp-style-engine.php
index 9698ce4f8796ab..07480766a2011b 100644
--- a/packages/style-engine/class-wp-style-engine.php
+++ b/packages/style-engine/class-wp-style-engine.php
@@ -223,7 +223,7 @@ class WP_Style_Engine {
 	 * @return string The slug, or empty string if not found.
 	 */
 	protected static function get_slug_from_preset_value( $style_value, $property_key ) {
-		if ( is_string( $style_value ) && strpos( $style_value, "var:preset|{$property_key}|" ) !== false ) {
+		if ( is_string( $style_value ) && str_contains( $style_value, "var:preset|{$property_key}|" ) ) {
 			$index_to_splice = strrpos( $style_value, '|' ) + 1;
 			return _wp_to_kebab_case( substr( $style_value, $index_to_splice ) );
 		}
@@ -390,7 +390,7 @@ protected static function get_css_declarations( $style_value, $style_definition,
 
 		// Build CSS var values from var:? values, e.g, `var(--wp--css--rule-slug )`
 		// Check if the value is a CSS preset and there's a corresponding css_var pattern in the style definition.
-		if ( is_string( $style_value ) && strpos( $style_value, 'var:' ) !== false ) {
+		if ( is_string( $style_value ) && str_contains( $style_value, 'var:' ) ) {
 			if ( ! $should_skip_css_vars && ! empty( $style_definition['css_vars'] ) ) {
 				$css_var = static::get_css_var_value( $style_value, $style_definition['css_vars'] );
 				if ( static::is_valid_style_value( $css_var ) ) {
@@ -410,7 +410,7 @@ protected static function get_css_declarations( $style_value, $style_definition,
 			}
 
 			foreach ( $style_value as $key => $value ) {
-				if ( is_string( $value ) && strpos( $value, 'var:' ) !== false && ! $should_skip_css_vars && ! empty( $style_definition['css_vars'] ) ) {
+				if ( is_string( $value ) && str_contains( $value, 'var:' ) && ! $should_skip_css_vars && ! empty( $style_definition['css_vars'] ) ) {
 					$value = static::get_css_var_value( $value, $style_definition['css_vars'] );
 				}
 
@@ -464,7 +464,7 @@ protected static function get_individual_property_css_declarations( $style_value
 
 			if ( $style_definition && isset( $style_definition['property_keys']['individual'] ) ) {
 				// Set a CSS var if there is a valid preset value.
-				if ( is_string( $value ) && strpos( $value, 'var:' ) !== false && ! $should_skip_css_vars && ! empty( $individual_property_definition['css_vars'] ) ) {
+				if ( is_string( $value ) && str_contains( $value, 'var:' ) && ! $should_skip_css_vars && ! empty( $individual_property_definition['css_vars'] ) ) {
 					$value = static::get_css_var_value( $value, $individual_property_definition['css_vars'] );
 				}
 				$individual_css_property                      = sprintf( $style_definition['property_keys']['individual'], $individual_property_key );