# PHP function description: decimal, binary, octal, and hexadecimal conversion functions

Source: Internet
Author: User
The first part of the Chinese character encoding Study Series. the PHP function is a detailed description of the conversion functions for decimal, binary, octal, and hexadecimal conversion. it mainly describes the conversion methods for each hexadecimal conversion to be used in actual development. 1. description of the decimal system conversion function
1. decimal to binary decbin () function, as shown in the following example:

Echo decbin (12); // output 1100
Echo decbin (26); // output 11010
Decbin
(PHP 3, PHP 4, PHP 5)
Decbin -- Convert decimal to binary
Description
String decbin (int number)
Returns a string containing the binary representation of the given number parameter. The maximum value to be converted is 4294967295 in decimal format, and the result is a string of 32 characters.

2. decimal to octal decoct () function

Echo decoct (15); // output 17
Echo decoct (264); // output 410
Decoct
(PHP 3, PHP 4, PHP 5)
Decoct -- Convert decimal to octal
Description
String decoct (int number)
Returns a string containing the octal representation of the given number parameter. The maximum value to be converted is 4294967295 in decimal format, and the result is 37777777777 ".

3. decimal to hexadecimal dechex () function

Echo dechex (10); // output
Echo dechex (47); // output 2f
Dechex
(PHP 3, PHP 4, PHP 5)
Dechex -- Convert decimal to hexadecimal
Description
String dechex (int number)
Returns a string containing the hexadecimal representation of the given number parameter. The maximum value to be converted is 4294967295 in decimal format, and the result is "ffffffff ".

II. binary system conversion functions
1, binary to hexadecimal to bin2hex () function

\$ Binary = "11111001 ";
\$ Hex = dechex (bindec (\$ binary ));
Echo \$ hex; // output f9
Bin2hex
(PHP 3> = 3.0.9, PHP 4, PHP 5)
Bin2hex -- Convert binary data to hexadecimal representation
Description
String bin2hex (string str)
Returns an ASCII string in hexadecimal notation of the str parameter. The byte mode is used for conversion. the byte level is higher than the byte level.

2. Convert binary to decimal bindec () function

Echo bindec ('20140901'); // output 51
Echo bindec ('20140901'); // output 51
Echo bindec ('20140901'); // output 7
Bindec
(PHP 3, PHP 4, PHP 5)
Bindec -- Convert binary to decimal
Description
Number bindec (string binary_string)
Returns the decimal value of the binary number represented by the binary_string parameter.
Bindec () converts a binary number to an integer. The maximum number of convertible values is 31-bit 1 or decimal 2147483647. PHP 4.1.0 starts. This function can process large numbers. in this case, it returns the float type.

III. description of octal system conversion functions
Octal to decimal Dec () function

Echo octdec ('77 '); // output 63
Echo octdec (decoct (45); // output 45
Octdec
(PHP 3, PHP 4, PHP 5)
Octdec -- convert octal to decimal
Description
Number octdec (string octal_string)
Returns the decimal equivalent of the octal value represented by the octal_string parameter. The maximum convertible value is 17777777777 or 2147483647 in decimal format. PHP 4.1.0 starts. This function can process large numbers. in this case, it returns the float type.

Hexadecimal to decimal hexdec () function

Var_dump (hexdec ("See "));
Var_dump (hexdec ("ee "));
// Both print "int (238 )"

Var_dump (hexdec ("that"); // print "int (10 )"
Var_dump (hexdec ("a0"); // print "int (160 )"
Hexdec
(PHP 3, PHP 4, PHP 5)
Hexdec -- Convert hexadecimal to decimal
Description
Number hexdec (string hex_string)
Returns the decimal number equivalent to the hexadecimal number indicated by the hex_string parameter. Hexdec () converts a hexadecimal string to a decimal number. The maximum value to be converted is 7 fffffff, that is, 2147483647 of the decimal number. PHP 4.1.0 starts. This function can process large numbers. in this case, it returns the float type.
Hexdec () replaces all non-hexadecimal characters with 0. In this way, all the zeros on the left are ignored, but the zeros on the right are included.

5. Any hexadecimal conversion base_convert () function

Echo base_convert (\$ hexadecimal, 16, 2); // output 101000110111001100110100
Base_convert
(PHP 3> = 3.0.6, PHP 4, PHP 5)

Base_convert -- convert a number between any hexadecimal values
Description
String base_convert (string number, int frombase, int tobase)
Returns a string containing the number in tobase format. The number is specified by frombase in hexadecimal notation. Both frombase and tobase can only be between 2 and 36 (including 2 and 36 ). Numbers higher than decimal digits are represented by the letter a-z. for example, a represents 10, B represents 11, and z represents 35.

Here, we mainly sort out the PHP hexadecimal conversion functions to facilitate development and search. for details about the functions, see The PHP Manual. Please pay attention to the next series of Chinese character encoding studies.
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