PHP ASCII码与字符串的相互转换的例子

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) {
56 $ud = (ord($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";
*/
$aa = new ascii;
echo "

&quot;;&lt;/p&gt; &lt;p&gt;echo $str = $aa-&gt;encode(&quot;PHP二次开发：www.php2.cc&quot;);&lt;/p&gt; &lt;p&gt;echo &quot;";
 
echo $aa->decode($str);
?>