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wp-content/plugins/jetpack-boost/app/lib/class-cache-compatibility.php

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+<?php
+/**
+ * Compatibility class for caching plugins.
+ */
+
+namespace Automattic\Jetpack_Boost\Lib;
+
+/**
+ * Compatibility class for caching plugins.
+ */
+class Cache_Compatibility {
+	/**
+	 * Checks if the site has a caching plugin.
+	 *
+	 * Supports:
+	 * - Endurance Page Cache
+	 *
+	 * @since 4.0.0
+	 *
+	 * @return bool True if the site has a caching plugin, false otherwise.
+	 */
+	public static function has_cache() {
+		/**
+		 * Filters whether the site has a caching plugin.
+		 * Useful for testing.
+		 *
+		 * @since 4.0.0
+		 *
+		 * @param bool $has_cache True if the site has a caching plugin, false otherwise.
+		 */
+		$has_cache = apply_filters( 'jetpack_boost_compatibility_has_cache', false );
+		if ( $has_cache ) {
+			return true;
+		}
+
+		/*
+		 * Disable Page Cache on sites that run Newfold's caching service.
+		 * Their cache is considered enabled when the endurance_cache_level option is set to 2 or 3.
+		 *
+		 * @link https://github.com/bluehost/endurance-page-cache/blob/59fe9993d2cb8a03d1df6da8325f73ad0851ba0a/endurance-page-cache.php#L343
+		 */
+		if (
+			class_exists( '\\Endurance_Page_Cache' )
+			&& 2 <= (int) get_option( 'endurance_cache_level' )
+		) {
+			return true;
+		}
+
+		return false;
+	}
+}