How to Run Your PHP4 Legacies

Every old PHP4 application faces this question: Does it also run under a newer PHP5 version? Hopefully you have migrated or deprecated all your legacy stuff already… or at least have customers that understand the value of a proper relaunch and are also willing to pay for it.

To make some customer fossils run on a PHP5 host, we did the following dirty hacks:

  • Set “AllowOverride All” in your Apache config in order to enable .htaccess files for runtime configuration.
  • Copy your legacy app on your new php5 host.
  • Place a .htaccess file in the directory containing something like this:
    php_flag register_globals on
    php_flag register_long_arrays on
    php_flag zend.ze1_compatibility_mode on
    php_flag short_open_tag on
    php_value auto_prepend_file "/home/web/my_legacy/_prepend.php"

    More info on configuration changes in php and list of ini-directives.

  • Place a file called _prepend.php in the same directory and set path info accordingly:
    // See also .htaccess file in this dir with more directives set for this site
    // Php4ify error reporting
    error_reporting(E_ERROR | E_WARNING | E_PARSE);
    // Add required include paths to some distant libs
    $path_arr = array();
    $path_arr[] = '/home/web/blah/libs/legacy';
    $path_arr[] = '/home/web/blah/libs/whatever';
    $path_str = implode(PATH_SEPARATOR, $path_arr);
    set_include_path( get_include_path() . PATH_SEPARATOR . $path_str);

This is indeed very very dirty and should only be considered as last-resort to make some legacy app runnable under php5 without having to do crazy search-and-replace orgies on old stuff.