Several commonly used string search functions in php

PHP SearchStringCommonly used functionsIntroduction, mainly introducing the use of strstr

1. strstr - Find the first occurrence of a string

string strstr ( string $haystack , mixed $needle [, bool $before_needle = false ] )
Note 1: $haystack is the string in question, $needle is the string being searched. This function is case-sensitive.
Note 2: The return value is from the beginning to the end of needle.
Note 3: Regarding $needle, if it is not a string, it is treated as an integer and used as the sequence number of the character.
Note 4: If before_needle is true, return the previous thing.

The code is as follows:

<?php 
$email = &#39;yuxiaoxiao@example.com&#39;; 
$domain = strstr($email, &#39;@&#39;); 
echo $domain; // 打印 @example.com 
$user = strstr($email, &#39;@&#39;, true); // 从 PHP 5.3.0 起 
echo $user; // 打印 yuxiaoxiao 
?>

2. stristr strstr case-insensitive version
3. 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 from. The numerical position returned is relative to the starting position of the haystack.
4. substr - returns the substring of the string

string substr ( string $string , int $start [, int $length ] )
$rest = substr("abcdef", -1 ); // Return "f"

Note 1: If start is a non-negative number, the returned string will start from the start position of string and start counting from 0. For example, in the string "abcdef", the character at position 0 is "a", the character at position 2 is "c", and so on.

Note 2: If start is a negative number, the returned string will start from the start character forward from the end of string.

Note 3: If the length of string is less than or equal to start, FALSE will be returned.

length

Note 4: If a positive length is provided, the returned string will include at most length characters from start (depending on the length of 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 will be returned.

Note 6: If length with a value of 0, FALSE or NULL is provided, an empty string will be returned.

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

The code is as follows:

<?php 
$rest = substr("abcdef", 0, -1); // 返回 "abcde" 
$rest = substr("abcdef", 2, -1); // 返回 "cde" 
$rest = substr("abcdef", 4, -4); // 返回 "" 
$rest = substr("abcdef", -3, -1); // 返回 "de" 
?>

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

string strrchr ( string $haystack, mixed $needle)

This function returns a part of the haystack string, which starts from the last occurrence of needle and ends at the end of haystack.

6. strripos - Calculate the position of the last occurrence of the specified string in the target string (not case sensitive)
7. stripos - Search The position where the string first appears (not sensitive to size)
8. strrpos - Calculate the position of the last occurrence of the specified string in the target string

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