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Need help understanding how these nested PHP "if" and "else" statements relate to one another.

LB1234
LB1234 asked
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Last Modified: 2014-01-07
The following code works, but I'd like to improve my understanding of the if and else statements.  How do the first and second else statement know which if they're related to?

Does the first else statement pertain to the if statement directly above it?  I know the second else statement relates to the very first IF statement but I don't understand why it's not relating to any of the other IF statements instead?

Thanks.

<?php
      $errors = array();  
		
		if(isset($_POST["submit"])) {
	  	$first_name = $_POST["first_name"];
	  	$last_name = $_POST["last_name"];
	  	$user_name = $first_name . "_" . $last_name;
	  	$access_level = $_POST["access_level"];
		$department = $_POST["department"];
		$password = $_POST["password"];
	  	$password2 = $_POST["password2"];
		 	
		 if ($password !== $password2) {
			$errors[] = "Passwords do not match, please re-enter";  
		 if (empty($password)) {
			 $errors[] = "Password is empty, please enter a password";
		 }
		 
		  } else {
			$query = "INSERT INTO users (first_name, last_name, user_name,  department, password, password2, access_level) VALUES (";
			$query .= "'{$first_name}', '{$last_name}', '{$user_name}',  '{$department}', '{$password}', '{$password2}', '{$access_level}')";
			$result = mysqli_query($connection, $query);
			mysqli_close($connection);
			redirect_to("account_created.php");
		  }
	} else {
  
	  	$first_name = "";
	  	$last_name = "";
	  	$user_name = "";
	  	$access_level = "";
		$department = "";
		$password = "";
	  	$password2 = "";
	  	$message = "Please log in";
	}



?>

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Commented:
First IF checks if the FORM has been submitted by checking if the SUBMIT value exists.
Second IF checks if the passwords match.  It then has a further IF to check if the password is empty (if so give a different error message)

If the form has been submitted and the passwords match and the passwords are not empty then add to database.

if(isset($_POST["submit"])) {
	// The form has been submitted
	if ($password !== $password2) {
		// If the passwords don't match set the error message

		if (empty($password)) {
			// If the password is empty then set a different error message
		}
	}
	else {
		// Add details to database
	}
}
else
{
	// first time the form has been loaded
	// set all values to blank
}

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Author

Commented:
Cathal, thanks, I understand that stuff.  I wrote this code.  But I don't fully understand the relationship between if and else statements.  Else statements are "contained" by IF statements, but I need to better understand how nesting works, and how to determine which else statements are contained by a particular if statement.  Why does the last else statement relate itself to first IF statement while the first else statement does not.  I guess I need to understand how nesting really works and why.

Author

Commented:
Also, ideally, should the 2nd and 3rd if statements be elseif statements?
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Top Expert 2014

Commented:
Else statements are "contained" by IF statements
No - else statements are part of an IF statement - they only fire if the IF condition is not true
To simplify your code - if the form has not been posted (i.e. the submit value is empty) then the ELSE part of the IF statement fires

if(isset($_POST["submit"])) {

}
else
{
      $first_name = "";
      ...
}
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Commented:
Yoder, you do realize there are novice coders out there who are doing their best and learning the ropes as they go, correct?  Labeling incorrect approaches as forms of "stupidity" has no place here.  For the benefit of the community stick to addressing the question asked and leave your unhelpful editorializing out of it.

Author

Commented:
Gr8, thanks for the explanation.  So if I'm reading you correctly, the second else statement actually applies to the SECOND if statement, even though it works sort of like its an if-else relationship between the first and the last else?  In the example above you indented out the if and the accompanying else statement, so I suppose that leaves the line 13 if to be paired up with line 26 else?


It's one of those situations where the code is technically broken but it still delivers the expected result?
gr8gonzoConsultant
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Commented:
I think yodercrm wasn't calling you stupid, but rather the common practice of putting braces on the same line as the "if" statement.

The spacing is just for readability. I'm not sure I understand what you mean by:
"even though it works sort of like its an if-else relationship between the first and the last else"
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Commented:
Ok very sorry yoder!  I misinterpreted what you meant.  OK I finally get it now.  The second if statement has a built in unseen else.  The third if statement has an else right below it, so the else go with that one.  The top if statement pairs up with the remaining else statement at the bottom.  

Got it now!
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Commented:
+1 for Python which will enforce coding standards!
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