<!DOCTYPE html>
<html>
<body>

<?php
$str = 'one,two,three,four';

// Áã limit
print_r(explode(',',$str,0));

// ÕýµÄ limit
print_r(explode(',',$str,2));

// ¸ºµÄ limit
print_r(explode(',',$str,-1));
?>

</body>
</html>