ProcessCacheLRU.php

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<?php
class ProcessCacheLRU {
    protected $cache = array(); // (key => prop => value)
    protected $cacheTimes = array(); // (key => prop => UNIX timestamp)

    protected $maxCacheKeys; // integer; max entries

    public function __construct( $maxKeys ) {
        $this->resize( $maxKeys );
    }

    public function set( $key, $prop, $value ) {
        if ( isset( $this->cache[$key] ) ) {
            $this->ping( $key ); // push to top
        } elseif ( count( $this->cache ) >= $this->maxCacheKeys ) {
            reset( $this->cache );
            $evictKey = key( $this->cache );
            unset( $this->cache[$evictKey] );
            unset( $this->cacheTimes[$evictKey] );
        }
        $this->cache[$key][$prop] = $value;
        $this->cacheTimes[$key][$prop] = time();
    }

    public function has( $key, $prop, $maxAge = 0 ) {
        if ( isset( $this->cache[$key][$prop] ) ) {
            return ( $maxAge <= 0 || ( time() - $this->cacheTimes[$key][$prop] ) <= $maxAge );
        }

        return false;
    }

    public function get( $key, $prop ) {
        if ( isset( $this->cache[$key][$prop] ) ) {
            $this->ping( $key ); // push to top
            return $this->cache[$key][$prop];
        } else {
            return null;
        }
    }

    public function clear( $keys = null ) {
        if ( $keys === null ) {
            $this->cache = array();
            $this->cacheTimes = array();
        } else {
            foreach ( (array)$keys as $key ) {
                unset( $this->cache[$key] );
                unset( $this->cacheTimes[$key] );
            }
        }
    }

    public function resize( $maxKeys ) {
        if ( !is_int( $maxKeys ) || $maxKeys < 1 ) {
            throw new UnexpectedValueException( __METHOD__ . " must be given an integer >= 1" );
        }
        $this->maxCacheKeys = $maxKeys;
        while ( count( $this->cache ) > $this->maxCacheKeys ) {
            reset( $this->cache );
            $evictKey = key( $this->cache );
            unset( $this->cache[$evictKey] );
            unset( $this->cacheTimes[$evictKey] );
        }
    }

    protected function ping( $key ) {
        $item = $this->cache[$key];
        unset( $this->cache[$key] );
        $this->cache[$key] = $item;
    }
}