PHP common functions - string

In the process of learning PHP, I compiled some commonly used functions. These are string functions.

header("Content-Type:text/html;charset=UTF-8");
//Remove both (unilateral) spaces or other predefined characters
$str = "##hello world@ @";
echo trim($str,'#,@')."
"; //hello world
echo ltrim($str,'#')."
" ; //hello world@@
echo rtrim($str,'@')."
"; //##hello world
/* chop() is an alias of rtrim()*/
/ /Return the directory part of the path
echo dirname("c:/testweb/home.php")."
"; //c:/testweb
/**String generation and conversion*/
// Fill the string into the specified string
$str = "hello world";
echo str_pad($str,20,'.',STR_PAD_BOTH)."
"; //.... hello world....
echo str_pad($str,20,'.',STR_PAD_LEFT)."
"; //....hello world
echo str_pad($ str,20,'.',STR_PAD_RIGHT)."
"; //hello world.........
//Reuse the specified string
echo str_repeat(".", 13)."
"; //.............
/* 13 is the number of repetitions*/
//Split the string into an array (including spaces , one space is 1 character)
$str = "my name is Junjun Liu";
$str1 = str_split($str,3);
print_r($str1); //Array ( [0] => my [1] => nam [2] => e i [3] => s J [4] => unj [5] => un [6] => Liu )
//Reverse the string
$str = "imagecreatetruecolor";
echo strrev($str)."
"; //roloceurtetaercegami
//Split the string according to the specified length
$ str = "An example on a long word is: Supercalifragulisticlasdkjflasdjfalsdkakd";
echo wordwrap($str,20, "
");
//Randomly scramble all the characters in the string (the numbers are scrambled The time interval symbols will also be shuffled)
$str = "a1,b2,c3";
echo str_shuffle($str)."
"; //1,ca32,b(random one kind)
//Parse the string into a variable
$str = "first=value&arr[]=foo+bar&arr[]=baz";
parse_str($str);
echo $first."
"; // value
echo $arr[0]."
"; // foo bar
echo $arr[1]."
"; // baz
print_r($ arr); //Array ( [0] => foo bar [1] => baz )
parse_str("id=23&name=John%20Adams",$myArray);
print_r($myArray); //Array ( [id] => 23 [name] => John Adams )
//Format numbers by thousandths group
echo number_format("1000000"); //1,000,000
echo number_format("1000000",2 ); //1,000,000.00
echo number_format("1000000",2,",","."); //1.000.000,00
//Case conversion
echo strtolower('NAME'); //name
echo strtoupper('name'); //NAME
echo ucfirst('my name is Junjun Liu'); //My name is Junjun Liu
echo ucwords('my name is Junjun Liu'); //My Name Is Junjun Liu
//html association tag
//Convert string to HTML entity
$str = "John & 'Adams'";
echo htmlentities($str, ENT_COMPAT); //John & 'Adams'
//Pre- Define character conversion to html encoding
htmlspecialchars($str);
echo "
";
//Replace n r and carriage return in the string with
tags to achieve newline output
$ string = "Thisrnisnranstringr";
echo nl2br($string);
/**
* This
* is
* a
* string
*/
//Strip HTML, XML, PHP tags
$str="asdasd< ;h3>woaini";
echo strip_tags($str); //asdasdwoaini
echo "
";
//Add a backslash before the specified character to escape the character in the string
$str = "Hello, My name is John Adams.";
echo addcslashes($str,'m'); //Hello, my name is John Adams
//Remove addcslashes backslashes
echo stripcslashes($str ); //Hello, my name is John Adams.
echo "

---

";
//Add a backslash before specifying the predefined characters
$str = "Who's John Adams?";
$str = addslashes($str);
echo $str; //Who's John Adams?
//Remove backslashes
echo stripslashes($str)."
"; //Who's John Adams?
// Add a backslash before some predefined characters in the string (all characters are escaped)
$str = "hello world.(can you hear me?)";
echo quotemeta($str)."< ;br/>"; //hello world.(can you hear me?)
//ASCII return character
echo chr(34); //Return "
//Return the ASCII code of the first character in the string Value
echo ord(abc); //97
echo "
";
/**String comparison*/
/*
* 1: The former is bigger
* -1: The latter is bigger
* 0: Equality before and after
*/
echo "Compare two strings without case sensitivity:".strcasecmp("abc","abd")."
"; //-1
echo "Compare two strings with case sensitivity:" .strcmp("abd","Abd")."
"; //1
echo "Compare two strings with case sensitivity:" .strncmp( "abcd","abcc",2)."
"; //0 /* 2 is the size of the first n strings compared*/
echo "Compare two strings without case sensitivity:". strncasecmp("abcd","abcc",4)."
"; //1
echo "Write and compare two strings in different sizes (in natural order):".strnatcmp("abc2"," abc12")."
"; //-1
echo "Write and compare two strings without distinguishing size (in natural order):".strnatcasecmp("Abc8","abc12")."< br/>"; //-1
/* String cutting and splicing*/
//Divide the string into small chunks (spaces also count)
$str="hello world hello world";
echo chunk_split($ str,2,"#"); //he#ll#o #wo#rl#d #he#ll#o #wo#rl#d#
//Cut the string
$first_token = strtok('/something ', '/');
$second_token = strtok('/');
var_dump($first_token); //string(9) "something"
var_dump($second_token); //bool(false)
// var_dump($first_token,$second_token);(Print two variables at the same time)
$str = "This is an /example string";
$tok = strtok($str,"/"); //This is an
echo $tok;
$str = "Thisisan /example string";
$tok = strtok($str,"/"); //Thisisan
echo $tok;
//Use one string to split another string for the logo
$data = "foo:*:1023:1000::/home/foo:/bin/sh";
list($user, $pass, $uid, $gid, $gecos, $home, $shell) = explode(":", $data);
echo $user; // foo
echo $pass; // *
//Concatenate the array values ​​into a string using predetermined characters
$array = array('lastname', ' email', 'phone');
$a = implode(",", $array);
echo $a; // lastname,email,phone
//Intercept string
$str = "absadf";
echo substr($str,2,3); //sad
echo substr($str,-4,-1);//sad
/* String search and replacement*/
//String replacement operation, size sensitive Write str_replace (replaced font, replaced string, original string)
$str = "1,2,3:4,5:6";
echo str_replace(",",":",$str) ."
"; //1:2:3:4:5:6
echo str_replace(array(",",":"),";",$str)."
"; //1;2;3;4;5;6
echo str_replace(array(",",":"),array(";","#"),$str)."< ;br/>"; //1;2;3#4;5#6
//String replacement operation, case-insensitive
$str = "abcdefg";
echo str_ireplace("ABC","xyz ",$str); //xyzdefg
//Count the number of times a string appears in another string substr_count (search in this string, the searched string, the starting offset position, specify the offset Maximum position)
$str1 = "name";
$str2 = "my name isname name";
echo substr_count($str2,$str1); //2
//Replace a certain segment of the string with another string
$var = 'ABCDEFGH:/MNRPQR/';
echo "Original: $var

---

n"; //Original: ABCDEFGH:/MNRPQR/
/* These two examples use "bob" to replace the entire $ var. */
echo substr_replace($var, 'bob', 0) . "
n"; //bob
echo substr_replace($var, 'bob', 0, strlen($var)) . "
n"; //bob
/* Insert "bob" at the beginning of $var. */
echo substr_replace($var, 'bob', 0, 0) . "
n"; //bobABCDEFGH:/MNRPQR/
/* The following two examples use "bob" to replace $var of "MNRPQR". */
echo substr_replace($var, 'bob', 10, -1) . "
n"; //ABCDEFGH:/bob/
echo substr_replace($var, 'bob', -7, -1) . "
n"; //ABCDEFGH:/bob/
/* Remove "MNRPQR" from $var.*/
echo substr_replace($var, '', 10, -1) . "
n"; //ABCDEFGH://
//Returns the similarity between two strings
$str1 = "abcdefgadfsa" ;
$str2 = "acdrgwsaasdf";
echo ((similar_text($str1,$str2)/strlen($str1))*100)."%"."
"; //58.333333333333%
//String search
$str = "zhangsan";
echo strstr($str,"a")."
"; //angsan starts from the front to find the position where a appears and intercepts it to the end ( Default false) Alias: strchr()
echo strstr($str,"a",true)."
"; //zh Start from the front to find the position where a appears and intercept it forward
echo strrchr( $str,"a")."
"; //an starts looking for a from the back and intercepts it to the end
echo strpos($str,"a")."
"; //2 Get the position where a appears for the first time in the string
echo strpos($str,"a",3)."
"; //6 Get the position where a appears in the string starting from position 3
echo strrpos($str,"a")."
"; //6 Get the position of the last occurrence of a in the string
//Convert the specified character
$trans = array("hello" => "hi", "hi" => "hello");
echo strtr("hi all, I said hello", $trans); //hello all, I said hi
echo strtr("baab", "ab ", "01"); //1001
$trans = array("ab" => "01");
echo strtr("baab", $trans); //ba01
/*
* strstr() : case sensitive
* stristr(): case insensitive
*/
/*
* strpos(): case sensitive
* stripos() case insensitive
* strrpos(): case sensitive
* strripos (): Case-insensitive
*
*/
//Returns the length of the first substring in the calculated string where all characters exist in the specified character set.
$var = strspn("42 is the answer to the 128th question.", "1234567890");
echo $var; //2 Because '42' is the first paragraph of subject and all characters exist in '1234567890' Continuous characters.
//Get the length of the starting substring of the unmatched mask
$a = strcspn('abcd', 'apple'); var_dump($a); //int(0)
$b = strcspn(' abcd', 'banana'); var_dump($a); //int(0)
$c = strcspn('hello', 'l'); var_dump($c); //int(2)
$d = strcspn('hello', 'world'); var_dump($d); //int(2)
/* String statistics*/
//Count the number of words contained in the string (third parameter??? ? ? ? ?
$str = "My name is John";
echo str_word_count($str); //4
print_r(str_word_count($str,1)); //Array ( [0] => My [1] => ; name [2] => is [3] => John )
print_r(str_word_count($str,2)); //Array ( [0] => My [3] => name [8] => is [11] => John )
//Count the length of the string
$str = ' ab cd ';
echo strlen($str); // 7
//Count the number of occurrences of all letters in the string ( 0,255), the number of occurrences of each character is represented by the corresponding ascii code value
$str = "aaaaasdfasdfwer;dlfgjjpoertuodbldbnlskjl;asfjoiwertowitwo";
echo "

";<br>//print_r(count_chars($ str));<br>echo "

";
//md5
$str = "hello4521";
echo md5($str); //5af267d811a324fd640b7ad2199dfe14
echo "

---

";
/ *
function getMd5($str){
return md5(md5($s)."tri");
}
*/
//md5_file()
$str = "ly.db";
echo md5_file($ str); //2f2b2262ed0732d497c90bf62af96240

The above has introduced the commonly used functions of PHP - strings, including PHP and string content. I hope it will be helpful to friends who are interested in PHP tutorials.