Question

I have an IF statement that consists of two separate function calls
passing values to two variables. Obviously if neither value is ‘FALSE’
then the code block is executed:

<?php
   class MyValidater {
      static function validateString($string) {
         if (preg_match("/[A-Za-z]+/", $string)) {
            return $string;
         } else {
            return false;
         }
      }
   }

   $firstName = "Daniel";
   $surname = "Simmons";

   // Dodgy IF statement
   if ($first = MyValidater::validateString($firstName) && $second = MyValidater::validateString($surname)) {
      print("Success: $first $second");
   } else {
      print("Fail: $first $second");
   }
?>

As you can see both the $first and $second variables should contain
the values held in $firstName and $surname after successfully being
validated by the Static method validateString.

However, the values of the two variables end up: $first = ‘1’ and
$second = “Simmons”.

The ‘1’ should be “Daniel” but for some reason $first is being passed
the value ‘1’ or TRUE. If you swap the two assignment statements over
so that $second is evaluated first, you end up with the opposite
outcome as before. $second = ‘1’ and $first = “Daniel”

Can anyone explain why the String value “Daniel” being returned from
the class method is being changed into the int ‘1’ for the first part
of the conditional statement only? I have had a quick look though the
PHP documentation but cannot find an explanation.

For the moment the workaround is to change the return value from the
static method to be true/false and then make $first = $firstName,
etc… upon success. But this involves more code and I would rather
find out why this way does not work.

Answer 1

You need to bracket your expressions:

if (($first = MyValidater::validateString($firstName)) && ($second = MyValidater::validateString($surname)))

What’s actually happening is this:

if ($first = (MyValidater::validateString($firstName) && $second = MyValidater::validateString($surname)))

It would be much clearer to just do this (note this code isn’t identical to what you have):

$first = MyValidater::validateString($firstName);
$second = MyValidater::validateString($surname);

if ($first && $second)