<?php

$re = '/class="(.*?)"|id="(.*?)"/s';
$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);

// Print the entire match result
print_r($matches);

?>