PHP零整数被评估为false

As the title says, PHP seems to be evaluating the integer value 0 as false.

Take for example this snippet:

http://sandbox.onlinephpfunctions.com/code/13d885fb68359a3154999c2ef85db7c913c49bc5

<?php

if($exists = checkDup()){
    echo $exits;
}
else{
    echo "error!";  
}

function checkDup ($foo = 'blah', $bar = 'blah'){
    if ($foo == $bar) return (int) 0;
    return false;
}

As you can see, despite casting the reply as an int PHP parsing the return as false which in incorrect.

PHP is evaluating a lot to false ;) For example null, '', 0 You have to include a type check as well, you can do so by using === or !==

$exists = checkDup();
if($exists !== false){
    echo $exits;
}
else{
    echo "error!";  
}

function checkDup ($foo = 'blah', $bar = 'blah'){
    if ($foo == $bar) return 0;
    return false;
}

You should use if($exists = checkDup() !== false)

0 == false; //true

0 === false; //false

When you don't specify the a boolean expression in the if, it will execute the == operator