ruser@bew42:~$ php -r ' if (preg_match("/[-+]?([0-9]*\.)?[0-9]+/", "-03.75") != 0) {echo "true\n";} else { echo "false\n"; }';
true
ruser@bew42:~$ php -r ' if (preg_match("/[-+]?([0-9]*\.)?[0-9]+/", "-x.75") != 0) {echo "true\n";} else { echo "false\n"; }';
true