src/PEAR/Registry.php
function isAlias($alias)
    {
        if (PEAR::isError($e = $this->_lock(LOCK_SH))) {
            return $e;
        }
        $ret = $this->_isChannelAlias($alias);
        $this->_unlock();
        return $ret;
    }
function isAlias($alias)
    {
        if (PEAR::isError($e = $this->_lock(LOCK_SH))) {
            return $e;
        }
        $ret = $this->_isChannelAlias($alias);
        $this->_unlock();
        return $ret;
    }
Determines whether the parameter is an alias of a channel
@param string
@return bool