<?php
$beer="libo";
echo "he drink some $beers";//输出he drink some
echo "<br>";
echo "he drink some ".$beer."s";//he drink some libos
echo "<br>";
echo "he drink some ${beer}s";//he drink some libos
echo "<br>";
echo "he drink some {$beer}s";//he drink some libos
echo "<br>";
//定界符
$string=<<<EOT
定界符中可以使用任意转义字符，直接使用双引号以及解析其中的变量
EOT;
echo $string;
echo "<br>";
//引号套引号
echo '"nihao"';//"nihao"
echo "<br>";
echo "\"nihao\"";//"nihao"
//NULL
$a=NULL;
$b="value";
unset($b);
var_dump($a);//NULL
var_dump($b);//NULL
var_dump($c);//NULL
?>
