Question

我需要一个正则表达式才能接受输入，只有在可能的情况下接受

1.它仅以字符开头[a-zA-Z]

2.它可能包含数字，但可能不会重复3次或更多次。

示例：

akjsjdfljsfjl133113有效

123123sfsf无效

asfsdf1111asdf无效 adf111无效

我试过这段代码

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

Answer 1

您可以在此处使用否定前瞻。

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

请参阅Live demo

正则表达式

^                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

PHP中的输入验证的正则表达式

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