Delimiter expressed by php regular expression

Before learning regular expressions, we must first learn the delimiters of regular expressions.

The delimiter is to set a boundary, and what is within the boundary is the regular expression.

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

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

Let’s take a few examples:

Note: \ is an escape character. If you need to match / in the regular expression later, as shown below:

/ / /

If you really want to match / at this time, you need to escape the / in the delimiter with an escape character and write it as the following example:

/ \/ /

If you find it troublesome, you can set two forward slashes (/ /) when encountering such characters that need to be escaped. delimiter, change it to another delimiter (# #).