doitinpoland.com/wp-content/plugins/sitepress-multilingual-cms/inc/cache.php

<?php

if ( ! defined( 'ICL_DISABLE_CACHE' ) ) {
	define( 'ICL_DISABLE_CACHE', false );
}

// phpcs:disable PEAR.NamingConventions.ValidClassName.Invalid
// phpcs:disable PEAR.NamingConventions.ValidClassName.StartWithCapital

/**
 * Class icl_cache
 */
class icl_cache {

	/** @var array */
	protected $data;

	/** @var string */
	protected $name;

	/** @var bool */
	protected $cache_to_option;

	/** @var bool */
	protected $cache_needs_saving;

	public function __construct( $name = '', $cache_to_option = false ) {
		$this->data               = [];
		$this->name               = $name;
		$this->cache_to_option    = $cache_to_option;
		$this->cache_needs_saving = false;

		$this->init();
	}

	public function init() {
		if ( $this->cache_to_option ) {
			$this->data = icl_cache_get( $this->name . '_cache_class' );
			if ( false === $this->data ) {
				$this->data = [];
			}

			add_action( 'shutdown', [ $this, 'save_cache_if_required' ] );
		}
	}

	public function save_cache_if_required() {
		if ( $this->cache_needs_saving ) {
			icl_cache_set( $this->name . '_cache_class', $this->data );
			$this->cache_needs_saving = false;
		}
	}

	public function get( $key ) {
		if ( ICL_DISABLE_CACHE ) {
			return null;
		}
		return isset( $this->data[ $key ] ) ? $this->data[ $key ] : false;
	}

	public function has_key( $key ) {
		if ( ICL_DISABLE_CACHE ) {
			return false;
		}
		return array_key_exists( $key, (array) $this->data );
	}

	public function set( $key, $value ) {
		if ( ICL_DISABLE_CACHE ) {
			return;
		}
		if ( $this->cache_to_option ) {
			$old_value = null;
			if ( isset( $this->data[ $key ] ) ) {
				$old_value = $this->data[ $key ];
			}
			if ( $old_value !== $value ) {
				$this->data[ $key ]       = $value;
				$this->cache_needs_saving = true;
			}
		} else {
			$this->data[ $key ] = $value;
		}
	}

	public function clear() {
		$this->data = array();
		if ( $this->cache_to_option ) {
			icl_cache_clear( $this->name . '_cache_class' );
		}
	}
}

if ( ! function_exists( 'icl_disable_cache' ) ) {
	function icl_disable_cache() {
		return defined( 'ICL_DISABLE_CACHE' ) && ICL_DISABLE_CACHE;
	}
}

if ( ! function_exists( 'icl_cache_get' ) ) {
	function icl_cache_get( $key ) {
		$result = false;
		if ( ! icl_disable_cache() ) {
			$icl_cache = get_option( '_icl_cache' );

			$result = isset( $icl_cache[ $key ] ) ? $icl_cache[ $key ] : false;
		}

		return $result;
	}
}

if ( ! function_exists( 'icl_cache_set' ) ) {
	function icl_cache_set( $key, $value = null ) {

		global $switched;
		if ( empty( $switched ) && ! icl_disable_cache() ) {
			$icl_cache = get_option( '_icl_cache' );
			if ( false === $icl_cache ) {
				$icl_cache = [];
				delete_option( '_icl_cache' );
			}

			if ( ! isset( $icl_cache[ $key ] ) || $icl_cache[ $key ] !== $value ) {
				if ( ! is_null( $value ) ) {
					$icl_cache[ $key ] = $value;
				} elseif ( isset( $icl_cache[ $key ] ) ) {
					unset( $icl_cache[ $key ] );
				}

				update_option( '_icl_cache', $icl_cache, 'no' );
			}
		}
	}
}

if ( ! function_exists( 'icl_cache_clear' ) ) {
	function icl_cache_clear( $key = false, $key_as_prefix = false ) {
		if ( ! icl_disable_cache() ) {
			/**
			 * @var WPML_Term_Translation $wpml_term_translations
			 * @var WPML_Post_Translation $wpml_post_translations
			 */
			global $wpml_term_translations, $wpml_post_translations;

			$wpml_term_translations->reload();
			$wpml_post_translations->reload();

			if ( false === $key ) {
				delete_option( '_icl_cache' );
			} else {
				/** @var array $icl_cache */
				$icl_cache = get_option( '_icl_cache' );

				if ( is_array( $icl_cache ) ) {
					if ( isset( $icl_cache[ $key ] ) ) {
						unset( $icl_cache[ $key ] );
					}

					if ( $key_as_prefix ) {
						$cache_keys = array_keys( $icl_cache );
						foreach ( $cache_keys as $cache_key ) {
							if ( strpos( $cache_key, $key ) === 0 ) {
								unset( $icl_cache[ $cache_key ] );
							}
						}
					}

					// Special cache of 'per language' - clear different statuses.
					if ( false !== strpos( $key, '_per_language' ) ) {
						foreach ( $icl_cache as $k => $v ) {
							if ( false !== strpos( $k, $key . '#' ) ) {
								unset( $icl_cache[ $k ] );
							}
						}
					}
					update_option( '_icl_cache', $icl_cache, 'no' );
				}
			}
		}
		do_action( 'wpml_cache_clear' );
	}
}

function w3tc_translate_cache_key_filter( $key ) {
	global $sitepress;

	return $sitepress->get_current_language() . $key;
}