The difference between characters and bytes in PHP and detailed graphic explanation of string and byte conversion

Characters in php are abstract entities that can be represented using a variety of different character schemes or code pages. A byte is a unit for transmitting information over a network (or storing information on a hard drive or in memory). This article also introduces examples of string and byte conversion in PHP through examples. Friends who are interested should take a look together

Characters:

Characters are abstract entities that can be represented using many different character schemes or code pages. For example, Unicode UTF-16 encoding represents characters as a sequence of 16-bit integers, while Unicode UTF-8 encoding represents the same characters as a sequence of 8-bit bytes. The common language runtime uses Unicode UTF-16 (Unicode Transformation Format, a 16-bit encoding) to represent characters.

In php, under UTF-8 encoding, a Chinese character occupies 3 characters, and under gbk encoding, it only occupies 2 characters.

Byte (Byte):

Byte is to transmit information through the network (or store information on the hard disk or memory) The unit.

Application:

If the table in the database is UTF8 encoded, and the field is set to a maximum of 10 characters, the maximum storage length is eg: 'I am in 1'

Let’s look at the PHP string and byte conversion example

<?php 
/** 
* byte数组与字符串转化类 
*/
class Bytes { 
/** 
* 转换一个String字符串为byte数组 
* @param $str 需要转换的字符串 
* @param $bytes 目标byte数组 
* @author Zikie 
*/
public static function getBytes($string) { 
$bytes = array(); 
for($i = 0; $i < strlen($string); $i++){ 
$bytes[] = ord($string[$i]); 
} 
return $bytes; 
} 
/** 
* 将字节数组转化为String类型的数据 
* @param $bytes 字节数组 
* @param $str 目标字符串 
* @return 一个String类型的数据 
*/
public static function toStr($bytes) { 
$str = &#39;&#39;; 
foreach($bytes as $ch) { 
$str .= chr($ch); 
} 
return $str; 
} 
/** 
* 转换一个int为byte数组 
* @param $byt 目标byte数组 
* @param $val 需要转换的字符串 
* 
*/
public static function integerToBytes($val) { 
$byt = array(); 
$byt[0] = ($val & 0xff); 
$byt[1] = ($val >> 8 & 0xff); 
$byt[2] = ($val >> 16 & 0xff); 
$byt[3] = ($val >> 24 & 0xff); 
return $byt; 
} 
/** 
* 从字节数组中指定的位置读取一个Integer类型的数据 
* @param $bytes 字节数组 
* @param $position 指定的开始位置 
* @return 一个Integer类型的数据 
*/
public static function bytesToInteger($bytes, $position) { 
$val = 0; 
$val = $bytes[$position + 3] & 0xff; 
$val <<= 8; 
$val |= $bytes[$position + 2] & 0xff; 
$val <<= 8; 
$val |= $bytes[$position + 1] & 0xff; 
$val <<= 8; 
$val |= $bytes[$position] & 0xff; 
return $val; 
} 
/** 
* 转换一个shor字符串为byte数组 
* @param $byt 目标byte数组 
* @param $val 需要转换的字符串 
* 
*/
public static function shortToBytes($val) { 
$byt = array(); 
$byt[0] = ($val & 0xff); 
$byt[1] = ($val >> 8 & 0xff); 
return $byt; 
} 
/** 
* 从字节数组中指定的位置读取一个Short类型的数据。 
* @param $bytes 字节数组 
* @param $position 指定的开始位置 
* @return 一个Short类型的数据 
*/
public static function bytesToShort($bytes, $position) { 
$val = 0; 
$val = $bytes[$position + 1] & 0xFF; 
$val = $val << 8; 
$val |= $bytes[$position] & 0xFF; 
return $val; 
} 
} 
?>

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