In the following code:$t = microtime(true);$now = DateTime::createFromFormat('U.u', $t);$now = $now->format("H:i:s.v");Trying to format() will return a fatal error if microtime(true) just so happened to return a float with all zeros as decimals. This is because DateTime::createFromFormat('U.u', $aFloatWithAllZeros) returns false.Workaround (the while loop is for testing if the solution works):$t = microtime(true);$now = DateTime::createFromFormat('U.u', $t);while (!is_bool($now)) {//for testing solution    $t = microtime(true);    $now = DateTime::createFromFormat('U.u', $t);}if (is_bool($now)) {//the problem    $now = DateTime::createFromFormat('U', $t);//the solution}$now = $now->format("H:i:s.v");

An easiest way to avoid error when microtime returns a non decimal float is to cast its result as a float using sprintf : $t = microtime(true);$now = DateTime::createFromFormat('U.u', sprintf('%f', $t));$now = $now->format("H:i:s.v");