It's necessary to clearly how to apply argument swapping when using an array of arguments. One might be tempted to use %0$ to reference $args[0].
In reality, the position specifier is always the array index+1:
$args[0] is referenced by %1$...
$args[1] is referenced by %2$...
etc.
Similarly, the first subpattern of a RegEx match would be found in $matches[1], the second in $match[2], etc. However if the $matches array is used as arguments to vsprint(), then the position specifier is subpattern+1:
preg_match( $pattern, $subject, $matches );
vsprintf( 'Full Match = %1$s, first Subpattern = %2$s, second Subpattern = %3$s', $matches );
