$re = '/<data_[a-zA-z]{3} .*?>/';
$str = '<data_let пробел**какие угодно символы кроме >
<data_abc asasgfgag12414.*asfasf>
<data_ABC asgasg>';
preg_match_all($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