requirements checking in core

// TODO: how can we detect pgsql version pre-PHP5?

I already posted some code here that works. Well, the version numbers might need to be extracted using a regexp (the result might be a string with additional information). Note that, for MySQL, it is also necessary to try out "SELECT VERSION()", since mysql_get_server_info might not be there.

About postgresql version, I've written a function in http://drupal.org/node/29082#comment-43377 some time ago, that does similar things as yours, but returns version as comparable integer and does not use pg_version() at all, so yours might be better.

Cross posting to a list of the error messages for requirement checking APIs.

Please help in reviewing
http://drupal.org/node/51772

Regarding safe_mode off requirement... is it really required?

_using_apache() function is not reliable. $_SERVER['SERVER_SOFTWARE'] may contain the word "apache", but apache_* functions are available only when PHP is running as an Apache module. apache_get_version() may fail. Sooner or later you would have to fix that. ;-)

Not sure how important it is to check for Apache version or modules, when Drupal can be installed on non-apache servers.

Maybe you could add code to check for PHP extensions using extension_loaded or get_loaded_extensions?

I love requirements checking. Does this checker assume that Drupal is up and working already? I'm hoping that it is like update.ph in that it works without a stovk settings.php - no DB connection. The most common use case IMO is "I just downloaded this drupal thing, is my site capable of running it?" What URL will this appear on?

Just suggestion, regarding version checking, hmm... let's say a contrib module works in PHP 4, but PHP 5 is not supported, yet. Or something that worked in (say) MySQL 3+ is now broken in MySQL 5, with no easy workaround, the contrib stuff might still be released with such "limitations"...

Actually, it is possible to specify a minimum_version, but what if a maximum_version check is required?

thanks for the clarification, jeremy. also thanks to webchick and jeremy for the nice error emssages. i will try ot oreview this one soon.

Regarding the comment about safe_mode... while, it may make things easier to avoid conflicts with file uploads et al, there are security issues involved. Changing safe_mode may not be an option as it cannot be changed in .htaccess files.

Instead of saying "it is recommended..." I would say something like "safe_mode is enabled, consider switching it off if you have problems with file uploads, but keep in mind safe_mode on is more secure. You might want to contact your hosting provider.". Yeah, I know it is not very well written, but I hope you get the idea. :-)

Great idea! There is an issue ready and waiting for someone to come in and clean up the error messages:

http://drupal.org/node/51772

Please post your feedback there, and try and tackle a few more while you're at it. ;)

Jeremy, a couple of E_NOTICES:

function_exists(version_compare) and function_exists(memory_get_usage)

Note the lack of (say) single quotes.

Aside from lack of single quotes... something wrong when checking for the PHP version?

function drupal_verify_version_php($version = array()) {
  if (!function_exists(version_compare) || 
      version_compare(phpversion(), $version['minimum_version'], '<')) {
    // version_compare() was added in PHP 4.1.
    drupal_set_message(t($version['message'], array('%minimum_version' => $version['minimum_version'], '%installed_version' => phpversion())), $version['required'] ? 'error' : 'status');
    if ($version['required']) {
      // invalid version of PHP
      return FALSE;
    }
  }
  // valid version of PHP, or we're just setting a warning.
  return TRUE;
}

If version_compare() does not exist, then that will return TRUE? However, if that happens, PHP version is lower than 4.1, hence it should return FALSE, or...?

Also, PHP (any version) is required, so maybe the check for $version['required'] could be removed?

Sorry, disregard (part of) my previous comment. I guess I had a boolean parser error when looking at the code. :-?

Maybe this is still valid however?

PHP (any version) is required, so maybe the check for $version['required'] could be removed?

Please use $error instead of $err.

Some strings can't be translated.

I'm a little bit shocked by the amount of code required to implement this. It's bigger than expected. drupal_verify_requirements_php() is a bit weird. I'm not yet convinced this is really needed, or whether this is the simplest approach. Looks a bit complicated.

I'm not a big fan of the "version guessing" (regex). It makes for ugly code.

$requirements_old["$new"] can be written as $requirements_old[$new].

Can format_size() be used instead of _shorthand_to_bytes()?

Here's some feedback regarding the way the database server version is determined in this issue's attachment "requirements_0.patch." You'll find code addressing these issues at the bottom of this post.

Won't it be good to give all Drupal components access to this functionality? I encourage this aspect of the requirements checking be placed in a centralized location, like database.inc. Similarly, it would be more usable if there would be one function, perhaps called db_get_server_version(), rather than one function per DBMS.

Your code strips "alpha", "beta", etc, but that can be relevant. version_compare() is designed to handle such terms.

It would be nice if the function cached the result so the database doesn't need to be queried over and over each time the function is called.

I wouldn't even bother checking pg_version() at this point. It's PHP 5 only and PostgreSQL 7.4 only. But more importantly, it isn't reliable because the 'server_version' element is missing (at least PHP 5.1.2). So cut to the chase and do the SELECT VERSION().

mysql_get_server_info() also doesn't exist prior to MySQL 4.0.1-alpha. So, it'd be handy to provide a SELECT VERSION() fallback when necessary.

So, here's the code I suggest using:

function db_get_server_version() {
  global $active_db, $db_type;
  static $prior_active_db, $version;

  if (!isset($active_db)) {
    drupal_set_message('Can\'t determine server version: database not connected.', 'error');
    return FALSE;
  }

  if (isset($version) && $prior_active_db == $active_db) {
    return $version;
  }
  $prior_active_db = $active_db;

  switch ($db_type) {
    case 'mysql':
    case 'mysqli':
      if (function_exists('mysql_get_server_info')) {
        // Since:  MySQL library: 4.0.1-alpha,  PHP: 4.0.5.
        $version = mysql_get_server_info($active_db);
      }
      else {
        $row = db_fetch_object(db_query('SELECT VERSION() AS version'));
        $version = $row->version;
      }
      $version = str_replace(array('-debug','-max','-nt','-opt'), '', $version);
      break;
    case 'pgsql':
      /*
       * Not using pg_version() because it is only available in
       * PHP 5 and with PostgreSQL library: 7.4.  More importantly,
       * the 'server_version' is missing, at least in PHP 5.1.2.
       */
      $row = db_fetch_object(db_query('SELECT VERSION() AS version'));
      $version = preg_replace('/^[^0-9]+([^ ]+).*/i', '\\1', $row->version);
      break;
    default:
      drupal_set_message('Can\'t determine server version: unknown $db_type.', 'error');
      $version = FALSE;
  }
  return $version;
}

went in with a different issue