Is it correct to create a variable within an if?

Question

it is correct to create a variable within an if ?

In the code below you create a variable within the if, and avoid using the same filter twice.

if($id = filter_input(INPUT_GET, 'id', FILTER_VALIDATE_INT)):
    /* Código */
endif;

What do you think of the practice within the IF? That’s against some PSR rule (PHP Standards Recommendation) ?

{Thank you}

Answer 1

First of all, the if is not a good example, because you can "create" the variable only once, even outside:

$id = filter_input(INPUT_GET, 'id', FILTER_VALIDATE_INT)
if( $id ):
   /* Código que usa o $id, sem "criar" de novo */
endif;

But in a while already complicates, so I’ll use this as an example:

while ($row = $result->fetch_row()) {
    printf ("%s (%s)\n", $row[0], $row[1]);
}

In this case, not only is it correct, but it is a example taken from the PHP manual.

Since in the while not only is it a common case, but often necessary, I see no reason not to use in the if. In the end, readability is always the most important thing. And for that, it only depends on the context where you will use it. In the above example there was certainly no gain in separating the lines.

If you have any PSR saying otherwise, you have to fix the PSR instead of complicating the code.