$re = '/^([_A-Za-z0-9-+]+(\.[_A-Za-z0-9-]+)*@[A-Za-z0-9-]+(\.[A-Za-z0-9]+)*(\.[A-Za-z]{2,})(;|$))*$/m';
$str = 'abc@damkovnai.un;efg@damkovnai.un;hij.kumar@damkovnai.un;klm.verma@damkovnai.un;
abc@damkovnai.un;efg@damkovnai.un;hij.kumar@damkovnai.un;klm.verma@damkovnai.un
abc@damkovnai.un;efg@damkovnai.un; hij.kumar@damkovnai.un ; klm.verma@damkovnai.un';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php