Question

Can’t get the point of === and !== with primitive types:

$a === $b TRUE if $a is equal to $b, and they are of the same type.
$a !== $b TRUE if $a is not equal to $b, or they are not of the same type.

The assuming that $request->getMethod() returns GET or POST (as string) and that $form->isValid() returns a boolean true or false, the following code:

if('POST' === $request->getMethod() || (false === $form->isValid())) :
endif;

Does make any sense in respect of this shorter one:

if('POST' == $request->getMethod() || !$form->isValid()) :
endif;

Answer 1

You have truty and falsy values in PHP. For instance, 0, '', array() are falsy values. If you use == it will match those values with the truty/falsy values:

var_dump(true == 'hello'); // true because a not empty string is a truty value
var_dump(false == 0); // true

=== will match not only the value but the type also:

var_dump(true === 'hello'); // false, true is a boolean and 'hello' a string
var_dump(false === 0); // false, false is a boolean and 0 is a string

This will become a problem when a function can return 0 or false, strpos for example.

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There are also other factors with the ==. It will type cast values to a int if you compare 2 different types:

var_dump("123abc" == 123); // true, because '123abc' becomes `123`

This will be problematic if you compare a password: http://phpsadness.com/sad/47