PHP中的輸入驗證的正則表達式

Question

我需要一個正則表達式，只接受輸入后的可能情況

1.它僅以字符開頭[a-zA-Z]

2.它可能包含數字，但可能不會重復3次或更多次。

示例 ：

akjsjdfljsfjl133113有效

123123sfsf無效

asfsdf1111asdf無效adf111無效

我試過這段代碼

$input_line="sfjs123232";
preg_match("/^[a-zA-Z](\d)\1{2,}/", $input_line, $output_array);

Answer 1

您可以在此處使用否定前瞻 。

^[a-zA-Z]+(?:(?!.*(\d)\1{2,}).)*$

查看現場演示

正則表達式

^                the beginning of the string
[a-zA-Z]+        any character of: 'a' to 'z', 'A' to 'Z' (1 or more times)
(?:              group, but do not capture (0 or more times)
 (?!             look ahead to see if there is not:
  .*             any character except \n (0 or more times)
  (              group and capture to \1:
   \d            digits (0-9)
  )              end of \1
   \1{2,}        what was matched by capture \1 (at least 2 times)
  )              end of look-ahead
  .              any character except \n
 )*              end of grouping
$                before an optional \n, and the end of the string