Update timestamp to microtime format

Author: Alex Westergaard

src/Analytics.php

@@ -80,15 +80,15 @@ public function setUserId(string $id)
     }
 
     /**
-     * @param int|float $microOrUnix
+     * @param int|float $microOrUnix time() or microtime(true)
      */
     public function setTimestamp($microOrUnix)
     {
         if (!is_numeric($microOrUnix)) {
             throw new GA4Exception("setTimestamp value must be numeric");
         }
 
-        $this->timestamp_micros = floor($microOrUnix * 1000);
+        $this->timestamp_micros = floor($microOrUnix * 1000000);
         return $this;
     }