1. String statistics and encryption
strlen($str): get the length of the string
str_word_count($str,$format,$charlist): count the number of words contained in the string
$format: an optional parameter that determines the format in which the statistical results are output
0 (default): directly return an integer number;
1: Output each word as a key value as a new index array;
2: Use the position where each word appears as the key name, each word as the key value, and output as a new array;
$charlist: optional parameter, additional string, the characters in which are counted as part of the word
md5($str): returns the encrypted string
2. Remove spaces or other strings
3. Editing of strings
Fourth, the splitting and splicing of strings
Five, string interception
Six, string find and replace
Seven, case conversion
Eight, string comparison
Nine, HTML tag association
ord($str): get the ASCII code value of a character
chr($ascii): Get the specified character according to the ASCII code value