Why does (0 == 'Hello') return true in PHP?

Question

Hey, if you have got the following code and want to check if $key matches Hello I\'ve found out, that the comparison always returns true

Answer 1

Because PHP does an automatic cast to compare values of different types. You can see a table of type-conversion criteria in PHP documentation.

In your case, the string "Hello" is automatically converted to a number, which is 0 according to PHP. Hence the true value.

If you want to compare values of different types you should use the type-safe operators:

$value1 === $value2;

or

$value1 !== $value2;

In general, PHP evaluates to zero every string that cannot be recognized as a number.