daniel has already posted about the slipiting part  , let me add the checking for space part als .

$pizza  = "piece1 piece2 piece3 piece4 piece5 piece6";
$pizaa = trim($pizza);
if(strpos($pizza,' ') >= 0)
{
    
$pieces = explode(" ", $pizza);
echo $pieces[0]; // piece1
echo $pieces[1]; // piece2
}else {
    echo $pizza;
}

Daniel has already posted about the splitting part, let me add the checking for space part also.

$pizza  = "piece1 piece2 piece3 piece4 piece5 piece6";
$pizza = trim($pizza); 

if(strpos($pizza, " ") !== false)
    
    $pieces = explode(" ", $pizza);
    echo $pieces[0]; // piece1
    echo $pieces[1]; // piece2 

}else{ 

    echo $pizza; 

}