Checks if a key exists.

@param  string $key
@return bool
16434
public function keyExists($key)
    {
        $exists = true;
        try {
            $this->get($key);
        } catch (Exception $e) {
            $exists = false;
        }
        return $exists;
    }
364032
public function offsetExists($key)
    {
        return isset($this->data[$key]) || array_key_exists($key, $this->data);
    }
88651
public function exists($key)
	{
		if(empty($this->meta)) return false;
		return array_key_exists($key, $this->meta);
	}
13512
public function exists(string $key): bool
    {
        $result = $this->execute([
            [
                'command' => 'get',
                'key' => $key,
                'result' => ['key']
            ]
        ]);
        return isset($result[0]['key']);
    }
439755
public function has(string $key): bool
    {
        $key = $this->getKey($key, true);
        return isset($this->headers[$key]);
    }
287853
public function offsetExists($key)
    {
        if (is_integer($key) && $key + 1 <= $this->count()) {
            return true;
        }

        return $this->has($key);
    }
375673
public function has($key): bool
    {
        return $this->exists($key) && null !== $this->attributes[$key];
    }
1032045
public function exists( $key ) {
		if ( ! $this->is_valid_session() ) {
			return false;
		}

		$key = $this->get_session_key( $key );
		if ( ! array_key_exists( $key, $_SESSION ) ) {
			return false;
		}

		return ! $this->_expired( $_SESSION[ $key ] );
	}
1316570
public function has($key) {
		$key = $this->extractKey($key);
		return isset($this->collection[$key]);
	}
1077463
public function has($key)
    {
        $flashMessages = $this->storage->get(self::FLASH_KEY);
        return isset($flashMessages[$key]);
    }
1272101
public function exists( $key ) {
		return ( is_array( $this->data ) && array_key_exists( $key, $this->data ) ) ||
			( is_object( $this->data ) && property_exists( $this->data, $key ) );
	}
301211
function has($key)
    {
        return (array_key_exists($key, $this->properties)) && $this->properties[$key] !== null;
    }
220977
public function containsKey($key)
    {
        if (!$this->enabled)
            return false;

        $has_key = array_key_exists($this->key($key), $this->cache);

        // $this->Logger->debug("Cache contains {$key}? " . (($has_key) ? 'TRUE' : 'FALSE'));

        return $has_key;
    }
52022
public function has($key)
    {
        $parts     = $this->getPath($key);
        $keyExists = true;
        $node      = $this->getFromCache();

        foreach($parts as $part) {
            $part = trim($part);

            if (!is_array($node) || !array_key_exists($part, $node)) {
                $keyExists = false;
                break;
            }

            $node = &$node[$part];
        }

        return ($keyExists);
    }
635966
public function has($key)
    {
        return isset($this->data[$key]) && is_array($this->data[$key]);
    }
1105983
public function has(string $key) : bool
    {
        return isset($this->collection[$this->useKey($key)]);
    }
376902
public function exists($key) {
        $key = $this->_encrypt($key);
        $data = $this->_memcached->get($key);
        
        return $data ? true : false;
    }