1.php單引號(hào)把內(nèi)容當(dāng)成純文本，不會(huì)解析里面的變量，但雙引號(hào)會(huì)解析里面的變量

   $foo = "data";
   echo '$foo';    //輸出$foo
   echo "$foo";   //輸出data

2.單引號(hào)不解析轉(zhuǎn)義字符，但'與\除外

echo 'it\'s a joke';    //輸出it‘s a joke
echo 'my \n name is';  // 輸出my \n name is
echo "my \n name is";  //輸出my name is