apcu_fetch - PHP code example

The PHP Function Apcu_Fetch

The php function apcu_fetch is an important one to understand, especially if you’re working with large projects. It’s an official replacement for the outdated APC extension, which used to offer both opcode caching and object caching functionality. After PHP began including its own opcache support, APCu took over and offers only the object caching functions.

APCu uses an array as its primary data storage method, which makes it a good option for applications that need to store and retrieve large amounts of data. However, there are also several alternative methods for caching objects in PHP that you should be familiar with. These alternatives include ObjectCache, Memcached, and XCache.

The error suppression operator @ allows you to wrap an expression in such a way that any errors that are directly caused by the expression will be suppressed. This is a useful feature for development purposes, but when used in production environments it can lead to performance issues because stock PHP systems tend to treat expressions that are wrapped with the error control operator in a less performant way than those that aren’t.

Namespaces are a concept in PHP that allow you to split up your code into distinct namespaces that can be accessed by your scripts without conflicting with each other. This is a similar concept to the operating system directories that namespace files, so that two files with identical names will exist in different locations on the filesystem. This helps you to keep your code organized and maintainable by preventing accidental code collisions between libraries that have been written by other developers.

apcu_fetch example

    public static function isSupported()
    {
        return \function_exists('apcu_fetch') && filter_var(\ini_get('apc.enabled'), \FILTER_VALIDATE_BOOL);
    }

    protected function doFetch(array $ids): iterable
    {
        $unserializeCallbackHandler = ini_set('unserialize_callback_func', __CLASS__.'::handleUnserializeCallback');
        try {
            $values = [];
            foreach (apcu_fetch($ids, $ok) ?: [] as $k => $v) {
                if (null !== $v || $ok) {
                    $values[$k] = null !== $this->marshaller ? $this->marshaller->unmarshall($v) : $v;
                }
            }

            return $values;
        } catch (\Error $e) {
            throw new \ErrorException($e->getMessage(), $e->getCode(), \E_ERROR, $e->getFile(), $e->getLine());
        } finally {
            ini_set('unserialize_callback_func', $unserializeCallbackHandler);
        }
    }

namespace Drupal\Component\FileCache;

/** * APCu backend for the file cache. */
class ApcuFileCacheBackend implements FileCacheBackendInterface {

  /** * {@inheritdoc} */
  public function fetch(array $cids) {
    return apcu_fetch($cids);
  }

  /** * {@inheritdoc} */
  public function store($cid, $data) {
    apcu_store($cid, $data);
  }

  /** * {@inheritdoc} */

  public function getApcuKey($cid) {
    return $this->binPrefix . $cid;
  }

  /** * {@inheritdoc} */
  public function get($cid, $allow_invalid = FALSE) {
    $cache = apcu_fetch($this->getApcuKey($cid));
    return $this->prepareItem($cache, $allow_invalid);
  }

  /** * {@inheritdoc} */
  public function getMultiple(&$cids, $allow_invalid = FALSE) {
    // Translate the requested cache item IDs to APCu keys.     $map = [];
    foreach ($cids as $cid) {
      $map[$this->getApcuKey($cid)] = $cid;
    }

    public function findFile($class)
    {
        // class map lookup         if (isset($this->classMap[$class])) {
            return $this->classMap[$class];
        }
        if ($this->classMapAuthoritative || isset($this->missingClasses[$class])) {
            return false;
        }
        if (null !== $this->apcuPrefix) {
            $file = apcu_fetch($this->apcuPrefix.$class, $hit);
            if ($hit) {
                return $file;
            }
        }

        $file = $this->findFileWithExtension($class, '.php');

        // Search for Hack files if we are running on HHVM         if (false === $file && defined('HHVM_VERSION')) {
            $file = $this->findFileWithExtension($class, '.hh');
        }

/** * Test if a cache is available for the given id and (if yes) return it (false else) * * WARNING $doNotTestCacheValidity=true is unsupported by the Apcu backend * * @param string $id cache id * @param boolean $doNotTestCacheValidity if set to true, the cache validity won't be tested * @return string cached datas (or false) */
    public function load($id, $doNotTestCacheValidity = false)
    {
        $tmp = apcu_fetch($id);
        if (is_array($tmp)) {
            return $tmp[0];
        }
        return false;
    }

    /** * Test if a cache is available or not (for the given id) * * @param string $id cache id * @return mixed false (a cache is not available) or "last modified" timestamp (int) of the available cache record */