Very illogical php value comparisons

Question

I stumbled upon a very strange bit of PHP code. Could someone explain why this is happening? *****BONUS POINTS***** if you can tell my why this is useful.

Answer 1

I don't see how ('a'==0) is helpful

$var = '123abc';

if (123 == $var)
{
    echo 'Whoda thunk it?';
}

It comes down to PHP's implicit conversion rules.

I'm failing at thinking of a practical example, but that's the basic reason why you're seeing that behavior.

Expansion:

In your example, 'a' is converted to 0 (zero), for the comparison. Imagine that for the purpose of the comparison, it's equivalent to '0a'. (That's the numeral zero, not the letter 'o.')

Further expansion:

I thought there was a good example use case for this in the manual, but I failed to find it. What I did come across should help shed some light on this "illogical" situation.

PHP is first and foremost a Web language, not a general-purpose scripting language. Since the Web is not typed and everything is a string, I had to do things slightly differently early on to make PHP do what people expected. Specifically, "123"==123 needs to be true in order to not have to type cast every single numeric user input.

http://bugs.php.net/bug.php?id=48012

That doesn't exactly answer the question, but it points in the general direction.