<?php
$name=123;
//Use the is series function to test whether the variable $name is an integer type
echo is_int($name) ;
$ss=false;
var_dump(is_bool($ss));
?>
echo is the output value.
var_dump is the type of printed value.
false, use echo to output, there is no value, so you can’t see the output. You can print the type with var_dump. Each variable has a type, so you can see the printed result.
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
echo is the output value.
var_dump is the type of printed value.
false, use echo to output, there is no value, so you can’t see the output. You can print the type with var_dump. Each variable has a type, so you can see the printed result.