Check if a given key is already configured for this extension.

@param string $key

@return bool
485177
protected function alreadyConfigured($key)
    {
        $config = $this->getClassMetadata()->getExtension($this->getExtensionName());

        return isset($config[$key]);
    }
439755
public function has(string $key): bool
    {
        $key = $this->getKey($key, true);
        return isset($this->headers[$key]);
    }
170730
public static function has( $key )
	{
		$cache = self::instance();
		if ( $cache ) {
			return $cache->isExisting( $key );
		}
		return false;
	}
389854
public function has($key) {
        $key = $this->getAbsoluteConfigKey($key);

        return array_has($this->config, $key);
    }
955785
public function containsKey(string $key): bool
    {
        if (isset($this->orgData[$key])) {
            return ! isset($this->removeAttributes[$key]);
        } else {
            return isset($this->addAttributes[$key]);
        }
    }
419000
public function has(string $key): bool
    {
        $this->checkConnection(__METHOD__);
        return $this->engine->has($key);
    }
249532
protected function nexmoConfigHas($key)
    {
        /** @var Config $config */
        $config = $this->app->make(Config::class);

        // Check for Nexmo config file.
        if (! $config->has('nexmo')) {
            return false;
        }

        return
            $config->has('nexmo.'.$key) &&
            ! is_null($config->get('nexmo.'.$key)) &&
            ! empty($config->get('nexmo.'.$key));
    }
1010373
public function offsetExists($key): bool
    {
        assert(
            is_string($key),
            sprintf('Invalid metadata key: (%s) %s', gettype($key), VarPrinter::toString($key))
        );

        return $this->has($key);
    }
162179
public function has($key): bool
    {
        return isset($this->items[$key]) || array_key_exists($key, $this->items);
    }
763943
public function has(string $key): bool
    {
        $result = $this->iterateConfig($key);

        return !($result === null);
    }
1300431
public function has($key)
    {
        return (bool) $this->redis->exists($this->redis->prefix($key));
    }
698705
public function exists(string $key): bool
    {
        return $this->handle->hExists($this->name, $key);
    }
669642
public function exists(string $key): bool
    {
        $key = $this->getKey($key);

        return cache()->has($key);
    }
568087
public function has($key)
    {
        $file = $this->getFileName($key);

        if ( !file_exists($file) )
        {
            return false;
        }

        // if cache file expire
        if ( filemtime($file) >= time() )
        {
            static::$keys[$key] = true;

            return true;
        }
        else
        {
            unset(static::$keys[$key]);
            unlink($file);

            return false;
        }
    }
727280
public function has(string $key): bool
    {
        return isset($this->data[$key]) || array_key_exists($key, $this->data);
    }
597948
public static function has(string $key) : bool
  {
    if ((new Cache)->retrieve($key) == null) return false;
    return true;
  }
4839
public function __isset($key)
	{
		if (isset($this->$key) && (!is_null($this->$key))) {
			return true;
		}
		if (!isset($this->specificationExtensions[$key])) {
			return false;
		}
		return !is_null($this->specificationExtensions[$key]);
	}