检查未知类型数是否为0的最安全方法是什么？ AKA为什么float（0）不等于（int）0？

Question

Can someone help me understand why this happens?

$zero = (float)0;
var_dump($zero);
var_dump(0);
var_dump( ($zero === 0) );

This produces:

float(0)
int(0)
bool(false)

I don't really understand why, I am aware of the giant red warning here , but isn't 0 supposed to be 0? Or is PHP actually comparing the variable type (float against int)?

Assuming that's the case, what is the safest way to check if a number (not knowing its exact type) is 0?

Thanks.

Answer 1

int(0) is same as float(0) , just that when you use === then type, as well as value, is compared. In this case value is same but type is different, hence its false . Those values are Equal but not Identical .

int(0) == float(0)    // true because only value is compared, which is same.
int(0) === float (0)  // false because even though value is same, type is also compared, which is different

$a === $b 'Identical' TRUE if $a is equal to $b, and they are of the same type.
$a == $b 'Equal' TRUE if $a is equal to $b after type juggling.

Reference:

A good way to test whether numeric value of your variable is 0 would be:

if (intval($zero)==0)
{
  // $zero is 0 in numeric terms. You can even send it a string to test, which will be 0
}

Read http://php.net/manual/en/types.comparisons.php

Answer 2

=== compares type as well as value. If you just want to compare value then use ==

$zero = (float)0;
var_dump($zero);
var_dump(0);
var_dump( ($zero === 0) );
var_dump( ($zero == 0) );

Will return float(0) int(0) bool(false) bool(true)

Answer 3

it's because === compares types and value and == compares only values

$foo = 0;

var_dump((float)$foo==(int)$foo); //Produces true

var_dump((float)$foo===(int)$foo); //Produces false

Answer 4

Actually their are two comparative operators

== checks only for equality of values

=== checks the equality of both type and the value.