character string String

String type

• Single quote string

• Double quote string

• nowdoc character string

• heredoc character string Example

<?php// 1、 Single quote string $str1 = 'hello world';var_dump($str1);// string(11) "hello world"// 2、 Double quote string $str2 = "hello world";var_dump($str2);// string(11) "hello world"// 3、nowdoc$str2 = <<<'EOD'hello worldEOD;var_dump($str2);// string(11) "hello world"// 4、heredoc$str1 = <<<EODhello worldEOD;var_dump($str1);// string(11) "hello world"

String escape

The system will deal with ： The backslash + Letter
for example ：

\r\n  Carriage returns 

PHP Escape characters commonly used in

\'   Display single quotation marks in single quotation string \"   Display double quotes in a double quote string \r   enter （ Go back to the beginning of the line ）\n   Line break \t  tab\$  $ stay PHP As a variable symbol 

The difference between single quotation mark and double quotation mark

1、 You can identify... In single quotation marks \' , And you can't recognize it in double quotation marks \'

<?php$str1 = 'hello \'world';$str2 = "hello \'world";var_dump($str1);// string(12) "hello 'world"var_dump($str2);// string(13) "hello \'world"

2、 Variable not recognized in single quotation marks , And double quotation marks can identify $ , Parse variables

• Variables in this province need to be distinguished from the following contents , Ensure variable independence

• Use variable identifiers to distinguish , Add a set of braces {}

<?php$a = 'Tom';$str1 = 'hello $a world';var_dump($str1);// string(14) "hello $a world"$str2 = "hello $a world";var_dump($str2);// string(15) "hello Tom world"$str3 = "hello $aworld";var_dump($str3);// PHP Notice:  Undefined variable: aworld$str4 = "hello {$a}world";var_dump($str4);// string(14) "hello Tomworld"

Rules for structurally defining string variables

1. The boundary character corresponding to the structured definition string is conditional

   • There cannot be anything after the upper delimiter
   • The bottom border character must be the leftmost top grid
   • The lower border character can only be followed by the symbol , Can't follow any characters
2. Structurally define the interior of a string （ Between boundary symbols ） All the content of is the string itself

<?php$str1 = <<<EODhello worldEOD;var_dump($str1);// string(11) "hello world"

String length

strlen(string $string): int

Example

<?php$str1 = 'hello world';$str2 = ' Hello world '; //  In Chinese utf8 Character set lower occupation 3 Bytes var_dump(strlen($str1)); // int(11)var_dump(strlen($str2)); // int(12)

Multi byte string extension module mbstring(Multi String)

<?php$str1 = 'hello world';$str2 = ' Hello world ';var_dump(mb_strlen($str1)); // int(11)var_dump(mb_strlen($str2)); // int(4)

String correlation function

1、 Conversion function
implode — Converts the value of a one-dimensional array to a string

implode(string $glue, array $pieces): stringimplode(array $pieces): stringprint_r(implode('|', [' Beijing ', ' Shanghai ', ' Guangzhou ']));//  Beijing | Shanghai | Guangzhou 

explode — Use one string to split another string

explode(string $separator, string $string, int $limit = PHP_INT_MAX): arrayprint_r(explode('|', ' Beijing | Shanghai | Guangzhou '));// Array// (//     [0] =>  Beijing //     [1] =>  Shanghai //     [2] =>  Guangzhou // )

str_split — Convert string to array

str_split(string $string, int $split_length = 1): array//  Be careful ： There is a problem with Chinese character splitting print_r(str_split('helloworld', 5));// Array// (//     [0] => hello//     [1] => world// )

2、 Intercept function
trim — Remove white space at the beginning and end of a string （ Or other characters ）

trim(string $str, string $character_mask = " \t\n\r\0\x0B"): string

ltrim — Remove the white space at the beginning of the string （ Or other characters ）

ltrim(string $str, string $character_mask = ?): string

rtrim — Remove the white space at the end of the string （ Or other characters ）

rtrim(string $str, string $character_mask = ?): string

Example

<?phpvar_dump(trim('  Hello , The world  '));// string(15) " Hello , The world "var_dump(ltrim('  Hello , The world  '));// string(16) " Hello , The world  "var_dump(rtrim('  Hello , The world  '));// string(16) "  Hello , The world "

substr — Returns a substring of a string

substr(string $string, int $offset, ?int $length = null): string//  Be careful ： There is a problem with Chinese character interception var_dump(substr('Hello World', 6, 5));// string(5) "World"

strstr — return haystack String from needle The string that first appears from the beginning to the end （ Take the file suffix ）

strstr(string $haystack, mixed $needle, bool $before_needle = false): stringvar_dump(strstr('Hello,World', 'W'));// string(5) "World"

3、 toggle case
strtolower — Convert a string to lowercase

strtolower(string $string): string

strtoupper — Convert a string to uppercase

strtoupper(string $string): string

ucfirst — Convert the first letter of a string to uppercase

ucfirst(string $str): string

Example

var_dump(strtolower('Hello, World'));// string(12) "hello, world"var_dump(strtoupper('Hello, World'));// string(12) "HELLO, WORLD"var_dump(ucfirst('hello, world'));// string(12) "Hello, world"

4、 Lookup function
strpos — return needle stay haystack First digit position in .

strpos(string $haystack, mixed $needle, int $offset = 0): intvar_dump(strpos('Hello, World', 'o'));// int(4)

strrpos — Return string haystack in needle The location of the last number .

strrpos(string $haystack, string $needle, int $offset = 0): intvar_dump(strrpos('Hello, World', 'o'));// int(8)

5、 Substitution function
str_replace — Substring replacement , The string or array is subject All of them search All be replace Results after replacement .

str_replace(    mixed $search,    mixed $replace,    mixed $subject,    int &$count = ?): mixedvar_dump(str_replace('o', 'A', 'Hello, World'));// string(12) "HellA, WArld"

6、 Format function
printf — Output formatted string

printf(string $format, mixed $args = ?, mixed $... = ?): int

sprintf — Returns a formatted string

sprintf(string $format, mixed ...$values): string

Format parameters ：https://www.php.net/manual/zh/function.sprintf.php

//  Direct output , Return to digital $ret1 = printf('my name is %s, and year old is %d', 'Tom', 18);// my name is Tom, and year old is 18var_dump($ret1); // int(34)//  Return string $ret2 = sprintf('my name is %s, and year old is %d', 'Tom', 18);var_dump($ret2);// string(34) "my name is Tom, and year old is 18"

7、 other
str_repeat — Duplicate a string

str_repeat(string $input, int $multiplier): stringecho str_repeat('ABC', 5);// ABCABCABCABCABC

str_shuffle — Randomly scramble a string

str_shuffle(string $str): stringecho str_shuffle('ABCDEFG');// GBEACDF

author ： Peng Shiyu

Game programming ️, A game development favorite ~

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