$re = '/class="(.*?)"|id="(.*?)"/ms';
$str = '<pre class="code-class" id="code-error">
function error_notice() {
?>
<div class="error notice">
<p><?php _e( \'There has been an error\', \'my_textdomain\' ); ?></p>
</div>
<?php
}
add_action( \'admin_notices\', \'my_error_notice\' );
</pre>';
preg_match_all($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