Why does PHP consider 0 to be equal to a string?

Question

I have the following piece of code:

$item[\'price\'] = 0;
/* Code to get item information goes in here */
if($item[\'price\'] == \'e\') {
    $item[\'price\'         


        

Answer 1

"ABC" == 0

evaluates true because first "ABC" is converted to integer and becomes 0 then it is compared to 0.

This is an odd behaviour of the PHP language: normally one would expect 0 to be promoted to string "0" and then compared to "ABC" with a result false. Perhaps that's what happen in other languages like JavaScript where the weak comparison "ABC" == 0 evaluates false.

Doing a strict comparison solves the problem:

"ABC" === 0

evaluates false.

But what if I do need to compare numbers as strings with numbers?

"123" === 123

evaluates false because the left and right term are of different type.

What is actually needed is a weak comparison without the pitfalls of PHP type juggling.

The solution is to explicit promote the terms to string and then do a comparison (strict or weak doesn't matter anymore).

(string)"123" === (string)123

is

true

while

(string)"123" === (string)0

is

false

---

Applied to the original code:

$item['price'] = 0;
/*code to get item information goes in here*/
if((string)$item['price'] == 'e') {
    $item['price'] = -1;
}