php正则绕过总结
    English Answer:
    Regular Expression Bypass Techniques in PHP.
    Regular expressions (regex) are a powerful tool for matching and manipulating text. They are used in a wide variety of applications, from simple text search and validation to complex data extraction and transformation. However, regex can also be complex and difficult to understand, and it is possible to write regex that is vulnerable to bypass attacks.
    A regex bypass occurs when an attacker is able to input data that matches the regex, but does not match the intended meaning. This can allow the attacker to bypass input validation, execute arbitrary code, or access unauthorized data.
    There are a number of different techniques that can be used to bypass regex. Some of the most common techniques include:
    Escaping characters: Regex characters can be escaped by using a backslash (\). This allows you to match characters that would otherwise be interpreted as regex operators. For example, the regex /\d+/ will match any sequence of one or more digits. However, the regex /\d+\./ will match any sequence of one or more digits followed by a period.
    Using character classes: Character classes allow you to match any character that belongs to a specific set. For example, the character class [0-9] matches any digit from 0 to 9. The character class [a-zA-Z] matches any letter from a to z or A to Z.
    Using quantifiers: Quantifiers allow you to specify the number of times a pattern can match. For example, the quantifier  matches the preceding pattern zero or more times. The quantifier + matches the preceding pattern one or more times.
    Using lookarounds: Lookarounds allow you to match patterns that are preceded or followed by specific other patterns. For example, the lookahead assertion (?=pattern) matches any pattern that is followed by the specified pattern. The lookbehind assertion (?<=pattern) matches any pattern that is preceded by the specified pattern.js正则表达式验证数字和字母
    Regex bypass attacks can be difficult to detect and prevent. However, there are a number of steps that you can take to reduce the risk of your applications being vulnerable to these attacks.
    Use a strong regex engine. A strong regex engine will be less likely to be vulnerable to bypass attacks.
    Validate your input data. Before using regex to process input data, you should validate the data to ensure that it is valid.
    Use a whitelist instead of a blacklist. A whitelist is a list of allowed patterns. A blacklist is a list of disallowed patterns. Whitelists are more secure than blacklists because they allow you to explicitly specify which patterns are allowed.
    Be careful when using regular expressions. Regex can be complex and difficult to understand. If you are not careful, you may write regex that is vulnerable to bypass attacks.
    Chinese Answer:
    PHP 正则绕过总结。
    正则表达式 (regex) 是一种强大的工具，用于匹配和操作文本。它们被用于各种各样的应用程序中，从简单的文本搜索和验证到复杂的数据提取和转换。然而，正则表达式也可能很复杂且难以理解，并且可以编写容易受到绕过攻击的正则表达式。
    当攻击者能够输入与正则表达式匹配但与预期含义不匹配的数据时，就会发生正则表达式绕过。这可能允许攻击者绕过输入验证、执行任意代码或访问未经授权的数据。
    有许多不同的技术可以用来绕过正则表达式。一些最常见的技术包括：
    转义字符， 正则表达式字符可以用反斜杠 (\) 转义。这允许您匹配将被解释为正则表达式运算符的字符。例如，正则表达式 /\d+/ 将匹配任何一个或多个数字的序列。然而，正则表达式 /\d+\./ 将匹配任何一个或多个数字后面跟着一个句点的序列。
    使用字符类， 字符类允许您匹配属于特定集合的任何字符。例如，字符类 [0-9] 匹配 0 到 9 之间的任何数字。字符类 [a-zA-Z] 匹配 a 到 z 或 A 到 Z 之间的任何字母。
    使用量词， 量词允许您指定模式可以匹配的次数。例如，量词  匹配前面的模式零次或多次。量词 + 匹配前面的模式一次或多次。
    使用环视， 环视允许您匹配前面或后面跟着特定其他模式的模式。例如，展望断言 (?=pattern) 匹配任何后面跟着指定模式的模式。回顾断言 (?<=pattern) 匹配任何前面跟着指定模式的模式。
    正则表达式绕过攻击可能很难检测和预防。但是，您可以采取一些步骤来降低应用程序容易受到这些攻击的风险。
    使用强大的正则表达式引擎。 强大的正则表达式引擎不太容易受到绕过攻击。
    验证您的输入数据。 在使用正则表达式处理输入数据之前，您应该验证数据以确保它是有效的。

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