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This article is about what PHP regular expressions do. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

PHP is widely used in the background CGI development of Web, usually getting some results after the user data, but if the data entered by the user is incorrect, there will be problems, such as someone's birthday is February 30th! Then how to check whether the summer vacation is correct? The support of PHP regular expressions makes it very convenient for us to match data.

Some concepts related to PHP regular expressions:

In a nutshell, regular expressions are a powerful tool for pattern matching and replacement. Find traces of regular expressions in almost all UNIX/LINUX-based software tools, such as Perl or PHP scripting languages. In addition, JavaScript, a client-side scripting language, also provides support for regular expressions, which have become a common concept and tool and are widely used by all kinds of technicians.

There is something like this on a Linux website: "if you ask Linux enthusiasts what they like best, he may answer regular expressions; if you ask him what he fears most, he will definitely say regular expressions except for tedious installation configuration."

As mentioned above, regular expressions look very complex and frightening, and most PHP beginners will skip here and continue to learn, but regular expressions in PHP have powerful functions that can use pattern matching to find qualified strings, determine whether strings meet conditions, or replace qualified strings with specified strings. It's a pity not to learn.

The basic syntax of PHP regular expressions:

A regular expression is divided into three parts: delimiters, expressions, and modifiers.

The delimiter can be any character other than a special character (such as "/!" Etc.), the common delimiter is "/". The expression consists of some special characters (see below for more details) and non-special strings, such as "[a-z0-9 characters -] + @ [a-z0-9 characters.] +" to match a simple e-mail string. Modifiers are used to turn on or off a function / mode. Here is an example of a complete regular expression:

/ hello.+?hello/is

The regular expression "/" above is the delimiter, the one between the two "/" is the expression, and the string "is" after the second "/" is the modifier.

If you have a delimiter in your expression, you need to use the escape symbol "\", such as "/ hello.+?\ / hello/is". Escape symbols can also execute special characters in addition to delimiters, and all special characters made of letters need to be escaped by "\", such as "\ d" for all numbers.

Thank you for reading! This is the end of this article on "what is the function of PHP regular expressions?". I hope the above content can be helpful to you, so that you can learn more knowledge. if you think the article is good, you can share it for more people to see!

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