$re = '/:[\d\w]+/';
$str = 'test2@gmail.com:123456
test2@hotmail.com:124554134
test1@yahoo.com:fdsfsdfe
test5@gmail.com:9875464';
preg_match_all($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