Why can the is series of functions only use the var_dump function to display the data type, but not echo?

Question

<?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));

?>

Answer 1

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.