Passing variables by reference

[RbgoWeb]

This function makes a copy of the argument passed to $str,
processes on the the copy which inside, could involve another copy.

function charEllipsis($str, $nchr)
{
if($nchr < 4) return;
if(strlen($str) > $nchr)
$str = substr($str, 0, ($nchr - 3)).'...';
return $str;
}

The return value is usually assigned to a variable and involves another copy like ...
$td = charEllipsis($msg, 32);
That makes a total of 2 or max 3x copying the value of $msg.

Now we modify the function to get strings by reference...
function charEllipsis(&$str, $nchr)//see the '&' ?
{
if($nchr < 4) return;
if(strlen($str) > $nchr)
$str = substr($str, 0, ($nchr - 3)).'...';
//the point of no return
}

and the function works directly on the original $msg value,
so doesn't need to copy it to a local variable,
so doesn't need to copy the local variable back to the caller. It only conditionally copies a modified version of $msg value over the original value inside the function, doing 0 or max 1x copy.
There's a lot of performance gained here, which is important on hi traffic sides presenting lots of data.