Introduction to common functions for finding strings in PHP

1. strstr - Find the first occurrence of a string

string strstr ( string $haystack , mixed $needle [, bool $before_needle = false ] )
Note 1: $haystack is the character in question String, $needle is the string being searched for. 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 serial number of the character.
Note 4: If before_needle is true, return the previous thing.

<?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 case-insensitive version of strstr
3. strpos - Find the first occurrence of a string

int strpos ( string $haystack , mixed $needle [, int $offset = 0 ] )
Note 1: The optional offset parameter can be used to specify which character in the 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 is provided with a value of 0, FALSE or NULL, 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.

<?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 the haystack character A part of a string starting from the last occurrence of needle and ending 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 - Find the position of the first occurrence of the string (not case-sensitive)
8. strrpos - Calculate the position of the last occurrence of the specified string in the target string

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