Introduction to strstr, strpos, substr, and strrchr for finding characters in php

In php, The strstr, strpos, substr, strrchr, and stripos functions are usually used to find out whether a character exists in a string. If you need to know about them, please refer to them.

1. strstr-first appearance of the search string

String strstr (string $ haystack, mixed $ needle [, bool $ before_needle = false])
Note 1: $ haystack is the string and $ needle is the string to be searched. This function is case sensitive.
Note 2: The return value starts from needle to the end.
Note 3: For $ needle, if it is not a string, it is used as an integer as the character serial number.
Note 4: If before_needle is true, the first thing is returned.

The Code is as follows:	Copy code
<? Php $ Email = 'yuxiaoxiao @ example.com '; $ Domain = strstr ($ email ,'@'); Echo $ domain; // print @ example.com $ User = strstr ($ email, '@', true); // starting from PHP 5.3.0 Echo $ user; // print yuxiaoxiao ?>

Ii. stristr strstr case-insensitive versions
Iii. strpos-find the position where the string first appears

Int strpos (string $ haystack, mixed $ needle [, int $ offset = 0])
Note 1: the Optional offset parameter can be used to specify which character in haystack to start searching. The returned numeric position is relative to the starting position of the haystack.
4. substr-return the substring of the string

String substr (string $ string, int $ start [, int $ length])
$ Rest = substr ("abcdef",-1); // return "f"

Note 1: If start is not negative, the returned string starts from the start position of string and starts from 0. For example, in the string "abcdef", the character at the position 0 is "a", and the character string at the position 2 is "c.

NOTE 2: If start is a negative number, the returned string starts from the start character at the end of the string.

NOTE 3: If the string length is less than or equal to start, FALSE is returned.

Length

Note 4: If a positive length is provided, the returned string will contain a maximum of length characters starting from start (depending on the length of the string ).

Note 5: if a negative length is provided, many characters at the end of the string will be missed (if start is a negative number, it will be counted from the end of the string ). If start is not in this text, an empty string is returned.

Note 6: If the length value is 0, FALSE, or NULL, an empty string is returned.

Note 7: If length is not provided, the returned substring starts from the start position until the end of the string.

The Code is as follows:	Copy code
<? Php $ Rest = substr ("abcdef", 0,-1); // return "abcde" $ Rest = substr ("abcdef", 2,-1); // return "cde" $ Rest = substr ("abcdef", 4,-4); // return "" $ Rest = substr ("abcdef",-3,-1); // return "de" ?>

 

5. strrchr-find the last occurrence of a specified character in the string

String strrchr (string $ haystack, mixed $ needle)

This function returns a part of the haystack string, starting with the last position of the needle until the end of the haystack.

6. strripos-calculate the position of the last occurrence of the specified string in the target string (Case Insensitive)
VII. stripos-locate the first occurrence of a string (no size difference)
VIII. strrpos-calculate the position of the last occurrence of a specified string in the target string

These functions only return whether the character you want to search for is saved in the string and return the position or 0 or 1, if you want to retrieve data from a specified position, you can use substr and other functions to combine them.