understanding nested ternary operators

Question

I have this piece of code that is unclear to me, specifically the complex use of the ternary operators

if (!$byField && is_numeric($v)){ // by ID
$r=$fromRow?
$fromRow:
($v?
dbRow("select * from pages where id=$v limit 1"):
array()
);
}

if someone could explain how to evaluate the nested use of ternary operators

Answer 1

Using nested ternary operators in your code adds unnecessary complexity. For the same reason, it should not be used. Just use a normal if-else block instead. That's far more readable.

if (condition) {
    # code...
} 
else {
    # code...
}

To answer your question:

$r = $fromRow ? $fromRow : ( $v ? dbRow("..."): array() );

The above statement can be rewrote as follows:

if (!$byField && is_numeric($v))
{ 
    if ($fromRow) 
    {
        $r = $fromRow;
    }
    elseif ($v) 
    {
        $r = dbRow("select * from pages where id=$v limit 1"):
    } 
    else 
    {
        $r = array();
    }
}

As you can see, it's more readable.

Answer 2

Consider the following code:

<?php
    $a = true;
    $b = false;
    $c = true;

    echo (
        $a 
        ? 'A is true'
        : (
            $b 
            ? 'A is false, but B is true'
            : (
                $c 
                ? 'A is false, B is false, but C is true'
                : 'A, B and C are all false'
            )
        )
    );
?>

Which could easily be rewritten as so:

<?php
    if ($a) {
        echo 'A is true';
    } else {
        if ($b) {
            echo 'A is false, but B is true';
        } else {
            if ($c) {
                echo 'A is false, B is false but C is true';
            } else {
                echo 'A, B and C are all false';
            }
        }
    }
?>

Answer 3

if (!$byField && is_numeric($v)){ // by ID
  if ($fromRow) {
    $r = $fromRow;
  else if ($v) {
    $r = dbRow("select * from pages where id=$v limit 1"):
  } else {
    $r = array();
  }
}