regex - Regular Expression capturing records PHP 2 -

i'm trying result below, can not, give me idea?

my cod.:

$string ='zamm et est hac pid pid sit amet, lacus nisi                   zppp scelerisque sagittis montes, porttitor ut arcu                 zamm tincidunt cursus eu amet nunc zamm c ac nunc, et pid pellentesque amet,                   zsss m urna scelerisque in vut';  if(preg_match_all("/zamm.*/", $string, $matches)) {     foreach($matches[0] $match){       echo $match;       echo "<br />";     } } 

expected result:

1: zamm et est hac pid pid sit amet, lacus nisi                   zppp scelerisque sagittis montes, porttitor ut arcu                 zamm tincidunt cursus eu amet nunc zamm c ac nunc, et pid pellentesque amet,                   zsss m urna scelerisque in vut  2: zamm tincidunt cursus eu amet nunc zamm c ac nunc, et pid pellentesque amet,                   zsss m urna scelerisque in vut  3: zamm c ac nunc, et pid pellentesque amet,                   zsss m urna scelerisque in vut 

/zamm(.(?!zamm))*/ 

take following characters not followed zamm. called negative lookahead.