PHP记录代码运行时间

class TimeCost{    private $cost = array();    private $record = array();    private $scale = 6;    public function __construct($scale = 6)    {        $this->cost = array();        $this->record = array();        $this->scale = $scale;    }    public function __toString()    {        return  $this->getString();    }    /**     * start to cal time.     *     * @param mixed $key     */    public function addCost($key)    {        $this->cost[$key] = microtime(true);    }    /**     * stop to cal time.     *     * @param mixed $key     */    public function closeCost($key)    {        $cost  = bcsub(microtime(true), $this->cost[$key], $this->scale);        if (in_array($key, array_keys($this->record))) {            $this->record[$key] = bcadd($cost, $this->record[$key], $this->scale);        } else {            $this->record[$key] = $cost;        }        return  $cost;    }        public function getString($key = null)    {        if ($key) {            return  "{$key}[{$this->record[$key]}]";        }        $str = '';        foreach ($this->record as $k => $v) {            $str .= "{$k}[{$v}]";        }        return  $str;    }}

$obj = new TimeCost();$token = 'test_a';$obj->addCost($token);some_code();$obj->closeCost($token);$reslut = $obj->getString($token);