PHP Functions: Mastering the Application of ord() and chr() Functions

PHP Functions: Mastering the Application of ord() and chr() Functions_PHP Tutorial

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Release： 2016-07-21 15:22:18

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The third issue of the Chinese character encoding research series, the PHP function chapter masters the application of ord() and chr() functions. In the previous issue [PHP Basics Chapter Detailed Explanation of ASCII Code Comparison Table and Character Conversion], we learned about the methods of ASCII code and character conversion, but When using it, I found that two special functions are needed for character conversion, which are used for conversion between characters and decimal. The ord() function converts characters into decimal numbers, and the chr() function converts decimal numbers into characters. In binary, Acts as a bridge between octal, decimal and hexadecimal.

1. Application of ord() function
ord() function is used to return the ASCII value of a character. The most basic usage is to obtain the ASCII value of a ord('a ') returns 97, but in actual development, it is most commonly used in the character interception function to obtain the decimal number of the high and low bit encoding of Chinese characters. For example, for common Chinese character interception functions, you can see the PHPWind or Discuz! forum source code. The principle of the substrs() function or cutstr() function is to obtain the ASCII code value of the character through the ord() function. If the return value is greater than 127, it is represented as half of the Chinese character, and then the second half is obtained and combined into a complete character, and combined at the same time Character encoding such as GBK or UTF-8, etc.

Take GBK encoding as an example and use the ord() function to judge Chinese characters and return the ASCII value of each Chinese character. The code is as follows

Copy code Code As follows:

 
$string = "Don't be obsessed with brother"; 
$length = strlen($string); 
var_dump($string);//Original Chinese 
var_dump( $length);//Length
$result = array(); 
for($i=0;$i<$length;$i++){ 
if(ord($string[$i] )>127){ 
$result[] = $string[$i].' '.$string[++$i]; 
} 
} 
var_dump($result); 

Code Description
1. Define a variable $string whose value is a string.
2. Get the length of the variable (number of bytes).
3. Print the variable and the variable The length is
4, obtain each byte value of the variable through a for loop, and display the two bytes of a Chinese character separated by a space.
The result is as shown below
php-ord-dec

Illustration: "Don't be obsessed with brother" is 5 Chinese characters, a total of 10 bytes (one Chinese character 2 characters section), each byte is printed separately and cannot be displayed normally as shown above

The initial value remains unchanged. Modify part of the code in the for loop to display the ASCII value of each byte

Copy code The code is as follows:

 
$result = array(); 
for($i=0;$i<$length;$i++){ 
if(ord( $string[$i])>127){ 
$result[] = ord($string[$i]).' '.ord($string[++$i]); 
} 
} 
var_dump($result); 

The above code uses the ord() function to print the ASCII value of each character, and the result is as follows
php-ord-dec-number

Through ord() After function conversion, the ASCII value of each character can be viewed normally.

2. Application of chr() function

The chr() function is opposite to the ord() function and is used to return the specified character, such as chr(97 ) returns a.

Combined with the above example, as long as the ASCII value of the Chinese character is obtained, the Chinese character can be assembled through the chr() function. The code is as follows

Copy code The code is as follows:

 
$string = "Don't be obsessed with brother"; 
$length = strlen($string); 
var_dump($string);//original Chinese
var_dump($length);//Length
$result = array(); 
for($i=0;$i<$length;$i++){ 
if(ord($string [$i])>127){ 
$result[] = ord($string[$i]).' '.ord($string[++$i]); 
} 
 } 
var_dump($result); 
foreach($result as $v){ 
$decs = explode(" ",$v); 
echo chr($decs[0]). chr($decs[1]); 
} 

The result is as shown below
php-chr-dec

The above code does not directly output Chinese characters, but prints out normal Chinese characters. The principle is to first obtain the ASCII value of each byte and use chr() The function converts it into bytes, and then combines the two bytes to form a complete Chinese character.

Through the discussion of the ord() and chr() functions, we have initially understood the encoding principle of Chinese characters, understood that one Chinese character has two bytes in GBK encoding, and used the ord() and chr() functions to implement various For the byte conversion method, please pay attention to the Chinese character encoding conversion principle in the next issue of the Chinese character encoding research series.

Reference materials
Performance comparison of PHPWind and Discuz interception character functions substrs and cutstr