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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:

ExampleExplanation
/Write regular in the middle/Correct
$Write regular in the middle$Correct
%Write the regular expression in the middle%Correct
^Write the regular expression in the middle^Correct
@Write regular in the middle@Correct
(Write regular in the middle)Error
A is written in the middle of regular expression A Error

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 (# #).


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