php 字符串怎么转成二进制字符串

<?php
header("Content-type:text/html;charset=utf-8");
/**
* 将字符串转换成二进制
* @param type $str
* @return type
*/
function StrToBin($str){
//1.列出每个字符
$arr = preg_split('/(?<!^)(?!$)/u', $str);
//2.unpack字符
foreach($arr as &$v){
$temp = unpack('H*', $v); 
$v = base_convert($temp[1], 16, 2);
unset($temp);
}
return join(' ',$arr);
//return $arr;
}
/**
* 讲二进制转换成字符串
* @param type $str
* @return type
*/
function BinToStr($str){
$arr = explode(' ', $str);
foreach($arr as &$v){
$v = pack("H".strlen(base_convert($v, 2, 16)), base_convert($v, 2, 16));
}
return join('', $arr);
}
echo StrToBin("php二次开发：www.php2.cc");;
echo '<br/>';
echo BinToStr("1110000 1101000 1110000 111001001011101010001100 111001101010110010100001 111001011011110010000000 111001011000111110010001 111011111011110010011010 1110111 1110111 1110111 101110 1110000 1101000 1110000 110010 101110 1100011 1100011");
?>