PHP strange == operator behavior

Question

PHP

Just wondering why the code

<?php echo 0 == 'sell'?'true':'false';

evaluates to true?

PHP 5.4.12, 5.3.19

Answer 1

because, the second argument in the == operator is cast to the type of the first argument, hence (int)'sell' === 0 hence 0 == 0 gives true.

Answer 2

The right operand is converted to number, more details here
php.net/manual/ru/language.operators.comparison.php

Answer 3

Not a bug. Use === when precision is important

Answer 4

And yet, for example, you cannot check the occurrence of a substring in a string using expressions like:

if (!strpos($haystack, $needle) {

because the string may begin with the substring you are looking for, and the function will return 0, which, without an explicit type comparison (operator ===), will not allow the condition to work correctly.
In general, PHP's loyalty to variable types can be the cause of some rather insidious bugs. So you need to have at least a basic understanding of comparing variables of different types in order not to step on this rake.

Answer 5

wrong thread, sorry