PHP实现ASCII码与字符串相互转换的方法

本文实例讲述了PHP实现ASCII码与字符串相互转换的方法。分享给大家供大家参考，具体如下：

<?php

class ascii {

/**

* 将ascii码转为字符串

* @param type $str 要解码的字符串

* @param type $prefix 前缀，默认:&#

* @return type

*/

function decode($str, $prefix="&#") {

$str = str_replace($prefix, "", $str);

$a = explode(";", $str);

foreach ($a as $dec) {

if ($dec < 128) {

$utf .= chr($dec);

} else if ($dec < 2048) {

$utf .= chr(192 + (($dec - ($dec % 64)) / 64));

$utf .= chr(128 + ($dec % 64));

} else {

$utf .= chr(224 + (($dec - ($dec % 4096)) / 4096));

$utf .= chr(128 + ((($dec % 4096) - ($dec % 64)) / 64));

$utf .= chr(128 + ($dec % 64));

}

return $utf;

}

/**

* 将字符串转换为ascii码

* @param type $c 要编码的字符串

* @param type $prefix 前缀，默认：&#

* @return string

*/

function encode($c, $prefix="&#") {

$len = strlen($c);

$a = 0;

while ($a < $len) {

$ud = 0;

if (ord($c{$a}) >= 0 && ord($c{$a}) <= 127) {

$ud = ord($c{$a});

$a += 1;

} else if (ord($c{$a}) >= 192 && ord($c{$a}) <= 223) {

$ud = (ord($c{$a}) - 192) * 64 + (ord($c{$a + 1}) - 128);

$a += 2;

} else if (ord($c{$a}) >= 224 && ord($c{$a}) <= 239) {

$ud = (ord($c{$a}) - 224) * 4096 + (ord($c{$a + 1}) - 128) * 64 + (ord($c{$a + 2}) - 128);

$a += 3;

} else if (ord($c{$a}) >= 240 && ord($c{$a}) <= 247) {

$ud = (ord($c{$a}) - 240) * 262144 + (ord($c{$a + 1}) - 128) * 4096 + (ord($c{$a + 2}) - 128) * 64 + (ord($c{$a + 3}) - 128);

$a += 4;

} else if (ord($c{$a}) >= 248 && ord($c{$a}) <= 251) {

$ud = (ord($c{$a}) - 248) * 16777216 + (ord($c{$a + 1}) - 128) * 262144 + (ord($c{$a + 2}) - 128) * 4096 + (ord($c{$a + 3}) - 128) * 64 + (ord($c{$a + 4}) - 128);

$a += 5;

} else if (ord($c{$a}) >= 252 && ord($c{$a}) <= 253) {

$ud = (ord($c{$a}) - 252) * 1073741824 + (ord($c{$a + 1}) - 128) * 16777216 + (ord($c{$a + 2}) - 128) * 262144 + (ord($c{$a + 3}) - 128) * 4096 + (ord($c{$a + 4}) - 128) * 64 + (ord($c{$a + 5}) - 128);

$a += 6;

} else if (ord($c{$a}) >= 254 && ord($c{$a}) <= 255) { //error

$ud = false;

}

$scill .= $prefix.$ud.";";

}

return $scill;

}

/*

PHP 转 ASCII

require_once "ascii_class.php";

*/