1.<?php
  echo false
  输出空 " "

2. 012转十进制 001 010=8+2=10
   0x12转十进制 0001 0010=16+2=18
   110转二进制 4+2=6
  
3. echo 1+1+1+'1+1+1' = 4
4.function change(){
      static $i = 0;
      $i++ ;
      return $i; 
   }
   print change();
   print change();
  //1 2
5.  heredoc 
    $a = 10;
    $b = <<<X
    <h1>$a is very much</h1>
    <h1>$a is very much</h1>
    X;
6.$a = 3;$b = 4;
  if($a||$b=5){
  echo 'tudo';
  }
  $b=4;短路运算
7.$array = array('1','1');
  foreach($array as $k=>$v){
        $v = 2;
  }
  $array所包含的值为array('1','1');不会改变原素组的值