PHP의 ASCII 코드 및 기본 변환 함수 예제 코드에 대한 자세한 설명

a字符的十进制：ord('a'); //输出97
二进制：decbin(ord('a')); //输出1100001
八进制：decoct(ord('a')); //输出141
十六进制：dechex(ord('a')); //输出61

采用实例一的方法获取a字符的二进制
decbin(ord('a'));
然后把二进制转换为十六进制或十进制
十六进制：bin2hex(decbin(ord('a')));//输出31313030303031
二进制J：bindec(decbin(ord('a'))); //输出97

class ascii
{
function decode($str)
{
    preg_match_all( "/(d{2,5})/", $str,$a);
    $a = $a[0];
    foreach ($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 $utf;
}
function encode($c)
{
    $len = strlen($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;
        }
        $scill .= "&#$ud;";
    }
    return $scill;
}