<?php
// reference
$one="test";
two=&$one;// It's the same as passing the address, and the two variables point to 1 An address
// Dynamic variables
$one="######";
$two="one";
$three="two";
echo $three."<br>";// The output "two"
echo $$three."<br>";// The output "one"
echo $$$three."<br>";// The output "######"
//php There are 8 A type of
//4 Kind of scalar: int integer
// bool boolean
// float,double,real
// string
//2 Species composite type: array
// object
//2 Special types: The resource type resource
// Empty type null
// Declaration of integers
$int=10; //10 Hexadecimal statement
$int=045;//8 Hexadecimal statement
$int=0xff;//106 Hexadecimal statement
$float=3.14E+5;// Scientific enumeration
$float=3.14E-5;
//1 is false In the case
$bool=false;
$bool=0;
$bool=0.000;
$bool=null;
$bool="";
$bool=" ";
$bool="0";
$bool=array();
// Declaration of strings
//1. Both single and double quotes can declare strings
//2. The declared string has no length limit
//3. In double-quoted strings, you can either parse variables directly or use escape characters directly ( You can escape the single quote itself or escape characters "\")
//4. In single-quoted strings, variables cannot be resolved directly, and escape characters cannot be used
//5. You can no longer use double quotes in double quotes and single quotes in single quotes
//6. It's best to use single quotes,
$str='aaaaa';
$str="aaaa";
// Delimiters declare strings, lots of strings
//test It's custom 1 String, can not have any character after, space can not
// Also want to test The end of this custom string cannot have any characters before the end
$str=<<<test
this write content......
test;
?>