php 转义字符的输出

<?php
$str = "\n";
if (ord($str) == 10) {//ord()返回str首字母的ascII码，int型
echo "\n "; //空白
echo "\\n ";//输出\n
echo "\\\n ";//输出\
echo "\$str ";//输出$str
echo "\t ";//空白
echo "\\t ";//输出\t

echo '\n '; //输出\n
echo '\\n ';//输出\n
echo '\\\n ';//输出\\n
echo '\$str ';//输出\$str
}
//无论在单引号还是在双引号里，要输出"\"都要写成"\\"