Implementation of PHP Regular Expression matching

Implementation of PHP Regular Expression matching

PHP Regular Expression matching is the final purpose of the application of regular expressions in PHP. How can we implement PHP Regular Expression matching? What are the specific methods used? Let's take a look at the specific content.

PHP inherits the tradition of UNIX and fully supports regular expression processing. Regular Expressions provide an advanced but not intuitive method for string matching and processing. Anyone who has used regular expressions in PERL knows that regular expressions are very powerful, but they are not so easy to learn.

PHP Regular Expression matching instance application:

 
 

  
  
^.+@.+..+$  
 
 

This effective but incomprehensible code is enough to make some programmers have a headache (I am) or let them give up using regular expressions. I believe that after reading this tutorial, you can understand the meaning of this Code.

PHP Regular Expression matching: Basic Pattern Matching

Everything starts from the most basic. Pattern is the most basic element of a regular expression. They are a set of characters that describe character strings. The mode can be very simple. It is composed of common strings and can be very complex. special characters are often used to indicate characters in a range, repeated occurrences, or context. For example:

^ Once

This mode contains a special character ^, indicating that this mode only matches strings starting with once. For example, this pattern matches the string "once upon a time" and does not match "There once was a man from NewYork. Like a ^ symbol, $ is used to match strings ending in a given pattern.

Bucket $

This mode matches "Who kept all of this cash in a bucket" and does not match "buckets. When both the character ^ and $ are used, it indicates exact match (the string is the same as the pattern ). For example:

^ Bucket $

Only matches the string "bucket ". If a mode does not include ^ and $, it matches any string containing this mode. Example: Mode

Once

And string

 
 

  
  
There once was a man from NewYork  
  
  
Who kept all of his cash in a bucket. 
 
 

Is matched.

In this mode, letters (o-n-c-e) are literal characters, that is, they indicate the letter itself, and numbers are the same. Escape sequences are used for other slightly complex characters, such as punctuation marks and white characters (spaces and tabs. All escape sequences start with a backslash. The escape sequence of the tab is t. So if we want to check whether a string starts with a Tab character, we can use this mode:

^ T

Similarly, n is used to represent a new line, and r is used to represent a carriage return. Other special symbols can be used in front with a backslash. For example, the backslash itself is represented by periods, and so on.

The PHP Regular Expression Matching content is introduced here. I hope you can understand and learn PHP Regular Expression matching.