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ord

(PHP 4, PHP 5, PHP 7)

ord转换字符串第一个字节为 0-255 之间的值

说明

int ord ( string $string )

解析 string 二进制值第一个字节为 0 到 255 范围的无符号整型类型。

如果字符串是 ASCII、 ISO-8859、Windows 1252之类单字节编码,就等于返回该字符在字符集编码表中的位置。 但请注意,本函数不会去检测字符串的编码,尤其是不会识别类似 UTF-8 或 UTF-16 这种多字节字符的 Unicode 代码点(code point)。

该函数是 chr() 的互补函数。

参数

string

一个字符。

返回值

返回 0 - 255 的整型值。

范例

Example #1 ord() 范例

<?php
$str 
"\n";
if (
ord($str) == 10) {
    echo 
"The first character of \$str is a line feed.\n";
}
?>

Example #2 检查 UTF-8 字符串的每一个字节

<?php
declare(encoding='UTF-8');
$str "🐘";
for ( 
$pos=0$pos strlen($str); $pos ++ ) {
 
$byte substr($str$pos);
 echo 
'Byte ' $pos ' of $str has value ' ord($byte) . PHP_EOL;
}
?>

以上例程会输出:


Byte 0 of $str has value 240
Byte 1 of $str has value 159
Byte 2 of $str has value 144
Byte 3 of $str has value 152

参见

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User Contributed Notes 3 notes

up
38
arglanir+phpnet at gmail dot com
6 years ago
As ord() doesn't work with utf-8, and if you do not have access to mb_* functions, the following function will work well:
<?php
function ordutf8($string, &$offset) {
   
$code = ord(substr($string, $offset,1));
    if (
$code >= 128) {        //otherwise 0xxxxxxx
       
if ($code < 224) $bytesnumber = 2;                //110xxxxx
       
else if ($code < 240) $bytesnumber = 3;        //1110xxxx
       
else if ($code < 248) $bytesnumber = 4;    //11110xxx
       
$codetemp = $code - 192 - ($bytesnumber > 2 ? 32 : 0) - ($bytesnumber > 3 ? 16 : 0);
        for (
$i = 2; $i <= $bytesnumber; $i++) {
           
$offset ++;
           
$code2 = ord(substr($string, $offset, 1)) - 128;        //10xxxxxx
           
$codetemp = $codetemp*64 + $code2;
        }
       
$code = $codetemp;
    }
   
$offset += 1;
    if (
$offset >= strlen($string)) $offset = -1;
    return
$code;
}
?>
$offset is a reference, as it is not easy to split a utf-8 char-by-char. Useful to iterate on a string:
<?php
$text
= "abcàê߀abc";
$offset = 0;
while (
$offset >= 0) {
    echo
$offset.": ".ordutf8($text, $offset)."\n";
}
/* returns:
0: 97
1: 98
2: 99
3: 224
5: 234
7: 223
9: 8364
12: 97
13: 98
14: 99
*/
?>
Feel free to adapt my code to fit your needs.
up
16
rowan dot collins at cwtdigital dot com
5 years ago
Regarding character sets, and whether or not this is "ASCII". Firstly, there is no such thing as "8-bit ASCII", so if it were ASCII it would only ever return integers up to 127. 8-bit ASCII-compatible encodings include the ISO 8859 family of encodings, which map various common characters to the values from 128 to 255. UTF-8 is also designed so that characters representable in 7-bit ASCII are coded the same; byte values higher than 127 in a UTF-8 string represent the beginning of a multi-byte character.

In fact, like most of PHP's string functions, this function isn't doing anything to do with character encoding at all - it is just interpreting a binary byte from a string as an unsigned integer. That is, ord(chr(200)) will always return 200, but what character chr(200) *means* will vary depending on what character encoding it is *interpreted* as part of (e.g. during display).

A technically correct description would be "Returns an integer representation of the first byte of a string, from 0 to 255. For single-byte encodings such as (7-bit) ASCII and the ISO 8859 family, this will correspond to the first character, and will be the position of that character in the encoding's mapping table. For multi-byte encodings, such as UTF-8 or UTF-16, the byte may not represent a complete character."

The link to asciitable.com should also be replaced by one which explains what character encoding it is displaying, as "Extended ASCII" is an ambiguous and misleading name.
up
12
v0rbiz at yahoo dot com
14 years ago
I did not found a unicode/multibyte capable 'ord' function, so...

<?php
function uniord($u) {
   
$k = mb_convert_encoding($u, 'UCS-2LE', 'UTF-8');
   
$k1 = ord(substr($k, 0, 1));
   
$k2 = ord(substr($k, 1, 1));
    return
$k2 * 256 + $k1;
}
?>
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