3v4l.org

run code in 300+ PHP versions simultaneously
<?php $string = 423.13; echo preg_replace_callback("/^(\d)([^\.]+)/", function($m){ return $m[1] . str_repeat(0, strlen($m[2])); }, $string);
Output for 5.5.0 - 5.5.35, 5.6.0 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.20, 7.2.0 - 7.2.33, 7.3.16 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.19, 8.3.0 - 8.3.7
400.13

preferences:
135.26 ms | 404 KiB | 216 Q