<?php
$string = 'Ruchika < ruchika@example.com >';
$pattern = '/[a-z0-9_-+.]+@[a-z0-9-]+.([a-z]{2,4})(?:.[a-z]{2})?/i';
preg_match_all($pattern, $string, $matches);
var_dump($matches[0]);
?>
<?php
$text = 'Ruchika < ruchika@example.com >';
preg_match_all("/[._a-zA-Z0-9-]+@[._a-zA-Z0-9-]+/i", $text, $matches);
print_r($matches[0]);
?>