求一正则表达式

Question

$patern="/^[a-z][a-z0-9\._-]*[^\._-]$/i";

Answer 1

$patern="/^[a-z][a-z0-9\._-]*[^\._-]$/i";
好象不对

Answer 2

$patern="/^[a-z][a-z0-9\._-]*[a-z0-9]$/i";

Answer 3

^[a-z][a-z0-9\._-]*[^\._-]$/i
哪里不对?

Answer 4

[^\._-] 包括了!@#$%^&*……这些符号吧

Answer 5

$pattern = "/^[a-z][\w\-\.]*[a-z\d]$/i"

Answer 6

$regExpr = '/^[a-z][\w-\.]*[^_-\.]$/i';