PHP Calculate execution time on code

Measure.php

<?php

class Measure
{
    /** @var array */
    protected static $timers;

    /**
     * Sets initial timer for specified name (optional)
     *
     * @param string $sName
     */
    public static function start(string $sName = 'defaults'): void
    {
        if (!self::$timers) {
            self::$timers = [];
        }

        self::$timers[$sName] = self::mt();
    }

    /**
     * Get elapsed time after start in seconds
     * Returns -1 in case of no current time started with name $sName
     *
     * @param string $sName
     *
     * @return float|int
     */
    public static function elapsed(string $sName = 'defaults')
    {
        $fStart = self::get($sName);
        if ($fStart == -1) {
            return $fStart;
        }
        $fEnd = self::mt();
        return $fEnd - $fStart;
    }

    /**
     * Get end time in seconds
     * Returns -1 in case of no current time started with name $sName
     *
     * @param string $sName
     *
     * @return float|int
     */
    public static function stop(string $sName = 'defaults')
    {
        $fEnd = self::elapsed($sName);
        if ($fEnd != -1) {
            unset(self::$timers[$sName]);
        }

        return $fEnd;
    }

    /**
     * Get initial timer for specified name
     * Returns -1 in case of no current time started with name $sName
     *
     * @param string $sName
     *
     * @return float|int
     */
    public static function get(string $sName = 'defaults')
    {
        if (!self::$timers || !array_key_exists($sName, self::$timers)) {
            return -1;
        }

        return self::$timers[$sName];
    }

    /**
     * Return current Unix timestamp with microseconds
     * @return float
     */
    public static function mt(): float
    {
        return microtime(true);
    }
}

Usage

Measure::start('paginate');
CustomPDF::addPagination($sFilePath, function($sFilePath) {
  $secs = Measure::stop('paginate');
  trace_log(sprintf('Execution time on paginate %s: %s seconds', $sFilePath, $secs));
});