Will side-effects be executed in this if clause

Question

Does the function add_new_user run the SQL INSERT query if it is inside the if clause?

I have the functions

function add_new_user ( $username, $email, $passhash_md5 )
{
    -- cut: database INSERT queries
    return 1;                                                                                                
}

I use the code above as

if ( validate( $username, $password, $email ) == 1 ) {
    if ( add_new_user ( $username, $email, $passhash_md5 )  == 1 ) {   
                // problem here
              -- cut
    }                                                                                                        
}

I asked this question because I am not sure why this handler always gives unsuccessful registraton notice. The two codes belong to the handler. The bug seems to be in the syntax of my code and perhaps in the use of if/else.

Answer 1

Does the function add_new_user run the SQL INSERT query if it is inside the if -clause?

Yes

function foo() {
  echo 'A';
  return true;
}

function bar() {
  echo 'B';
  return false;
}

if ( foo() ) {
  if ( bar() ) {
    echo 'C';
  }
}
// Output: AB

Answer 2

Yes

The function first get's evaluated for it's return value.

After the return value is known, the return value is compared to the integer value 1.

Answer 3

Yes. Anything between the if ( and the ) { is run to see if it is true. You can do anything in here really.

Answer 4

PHP has to evaluate the boolean expression in order to know if it will execute the block or not. So, to evaluate the "==" operator, it needs to evaluate both sides, including the function "add_new_user".

So, the answer is: yes, it will evaluate the function add_new_user AND it will execute the insert operation (unless you have some code inside add_new_user that will block this).

However, you are doing something that should be avoided when possible: you are using a condition with side-effects! This will give you headaches (for example, right now!).