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Introduction notes to PHP zero Foundation (11): String

2022-04-21 12:22:00 【Peng Shiyu psy】

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 $str2 = <<<'EOD' hello world EOD; var_dump($str2); // string(11) "hello world" // 4、heredoc $str1 = <<<EOD hello world EOD; var_dump($str1); // string(11) "hello world" 
     
    
      
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String escape

The system will deal with ： The backslash + Letter

for example ：

\r\n  Carriage returns 

     
    
      
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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 


     
    
      
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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" 
     
    
      
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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" 
     
    
      
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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 $str1 = <<<EOD hello world EOD; var_dump($str1); // string(11) "hello world" 
     
    
      
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String length 

strlen(string $string): int

     
    
      
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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) 
     
    
      
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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) 
     
    
      
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String correlation function

1、 Conversion function

implode — Converts the value of a one-dimensional array to a string 

implode(string $glue, array $pieces): string
implode(array $pieces): string

print_r(implode('|', [' Beijing ', ' Shanghai ', ' Guangzhou ']));
//  Beijing | Shanghai | Guangzhou 


     
    
      
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explode — Use one string to split another string 

explode(string $separator, string $string, int $limit = PHP_INT_MAX): array


print_r(explode('|', ' Beijing | Shanghai | Guangzhou '));
// Array
// (
// [0] =>  Beijing 
// [1] =>  Shanghai 
// [2] =>  Guangzhou 
// )


     
    
      
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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
// )

     
    
      
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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

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

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

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

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

     
    
      
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Example 

<?php var_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 " 
     
    
      
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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"

     
    
      
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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): string

var_dump(strstr('Hello,World', 'W'));
// string(5) "World"

     
    
      
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3、 toggle case

strtolower — Convert a string to lowercase 

strtolower(string $string): string

     
    
      
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strtoupper — Convert a string to uppercase 

strtoupper(string $string): string

     
    
      
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ucfirst — Convert the first letter of a string to uppercase 

ucfirst(string $str): string

     
    
      
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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"

     
    
      
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4、 Lookup function

strpos — return needle stay haystack First digit position in .

strpos(string $haystack, mixed $needle, int $offset = 0): int

var_dump(strpos('Hello, World', 'o'));
// int(4)

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

strrpos(string $haystack, string $needle, int $offset = 0): int

var_dump(strrpos('Hello, World', 'o'));
// int(8)

     
    
      
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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 = ?
): mixed

var_dump(str_replace('o', 'A', 'Hello, World'));
// string(12) "HellA, WArld"

     
    
      
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6、 Format function

printf — Output formatted string 

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

     
    
      
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sprintf — Returns a formatted string 

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

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


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

     
    
      
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7、 other

str_repeat — Duplicate a string 

str_repeat(string $input, int $multiplier): string

echo str_repeat('ABC', 5);
// ABCABCABCABCABC

     
    
      
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str_shuffle — Randomly scramble a string 

str_shuffle(string $str): string

echo str_shuffle('ABCDEFG');
// GBEACDF

     
    
      
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版权声明
本文为[Peng Shiyu psy]所创，转载请带上原文链接，感谢
https://yzsam.com/2022/04/202204211109376098.html

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