Introduction to regular expressions in PHP development basic tutorial

1. Regular application scenarios

• Matching email, mobile phone number, verification code

• Replace sensitive keywords. For example: Collection of articles involving politics and swearing words

• .

• Early expression replacement technology, UBB file encoding, markdown editor replacement, etc.

• In the future, you will also need to use regular expressions when writing your own template engines Show
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2. Delimiters of regular expressions

Let’s learn Let’s take a look at the regular delimiter. The so-called delimiter is to set a boundary, and what is within the boundary is the regular expression.

The regulations of PHP's regular expression delimiters are as follows:

delimiter, a-zA-Z0-9\ cannot be used, and others can be used. They must appear in pairs, with a beginning and an end.

Let’s take a look at a few examples

Note: \ is an escape character, if you need to match it in the regular expression later /, as follows:

/ / /

If you really want to match / at this time, you need to convert the / in the delimiter Escape the free characters and write it as the following example:

/ \/ /

If you find it troublesome, you need to convert When defining characters, you can delimit the two forward slashes (/ /) and change them to other delimiters (# #)