Detailed explanation of ASCII code comparison table and character conversion in PHP_PHP tutorial

PHP Basics explains in detail the ASCII code comparison table and character conversion, discusses the ASCII code comparison table diagram and the method of converting characters into decimal, octal, hexadecimal and HTML

General ASCII code Comparison table

Illustrated ASCII code comparison table, taking character A as an example
Dec represents decimal, such as 65
Hx represents hexadecimal, such as 41
Oct represents octal, such as 101
Char represents display characters, such as A

The ASCII code comparison table is divided into two units
1. Control characters 0-31 and 127
2. Can display characters 32-126
(1) 48~57 are ten Arabic numerals from 0 to 9;
(2) 65~90 are 26 uppercase English letters;
(3) Numbers 97 to 122 are 26 lowercase English letters;
(4) Other punctuation marks, arithmetic symbols, etc.;

2. ASCII extension code comparison table

3. Description of PHP character conversion function

For specific character conversion function descriptions, please refer to [PHP Functions Detailed Description of Decimal, Binary, Octal and Hexadecimal Conversion Functions]
Decimal to binary conversion decbin() function
Decimal to octal decoct() function
Decimal to hexadecimal dechex() function
Binary to hexadecimal bin2hex() function
Binary to decimal conversion bindec() function
Octal to decimal octdec() function
Hexadecimal to decimal hexdec() function
Arbitrary base_convert() function

Character conversion example
Example 1, how to convert a character to binary, octal or hexadecimal, you can use the ord() function to first convert the character into an ASCII value, and then use the corresponding base conversion function to convert, as follows
a This character is converted to its binary/octal/hexadecimal form as follows
Decimal notation of a character: ord('a'); //Output 97
Binary: decbin(ord('a')); //Output 1100001
Octal: decoct(ord('a')); //Output 141
Hexadecimal: dechex(ord('a')); //Output 61

Then you can check it by comparing the output results of each base with the ASCII code comparison table above.

Example 2, how to convert a binary to hexadecimal or decimal, such as the binary of a, as follows
Use the method of Example 1 to obtain the binary value of a character
decbin(ord('a'));
Then convert binary to hexadecimal or decimal
Hexadecimal: bin2hex(decbin(ord('a')));//Output 31313030303031
Binary J:bindec(decbin(ord('a'))); //Output 97

The ord() function discussed above will be discussed in detail in the next issue of the Chinese character encoding research series.

Four, reference materials
PHP function article explains the decimal, binary, octal and hexadecimal conversion functions in detail
asciitable comparison table
Wikipedia ASCII
Baidu Encyclopedia ASCII

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