PHP: Can an array have an array as a key in a key-value pair?

Question

I'm getting an "Illegal offset type" for this array:

public static $CATS_AND_TYPES = array(

        // Statement Administration
        array( self::CAT_STATEMENT_ADMIN => "Document Administration" ) => array(
            self::TYPE_STATEMENTS_LOADED => "Documents Loaded",
            self::TYPE_STATEMENTS_REMOVED => "Documents Removed"
        ),

        // Cron Jobs
        array( self::CAT_CRON_JOBS => "Cron Jobs" ) => array(
            self::TYPE_CRON_BULLETIN_RUN => "Bulletin Cron Job Ran",
            self::TYPE_CRON_EMAILER_RUN => "Emailer Cron Job Ran",
            self::TYPE_CRON_SURVEY_RUN => "Survey Cron Job Ran",
            self::TYPE_CRON_JOURNEY_RUN => "Journey Cron Job Ran",
            self::TYPE_CRON_DOCUMENT_RUN => "Document Cron Job Ran"
        ),

        // Global Administration
        array( self::CAT_GLOBAL_ADMIN => "Global Administration" ) => array(
            self::TYPE_GLOBAL_MAINTENANCE => "Global Maintenance",
            self::TYPE_GLOBAL_EMAIL_SENDING => "Email Sending"
        ),

        // Email Administration
        array( self::CAT_EMAIL_ADMIN => "Email Administration" ) => array(
            self::TYPE_EMAIL_SENT => "Email Sent",
            self::TYPE_EMAIL_RESENT => "Email Resent",
            self::TYPE_EMAIL_REMOVED => "Email Removed"
        ),

        // DCVs Administration
        array( self::CAT_DCVS_ADMIN => "DCVs Administration" ) => array(
            self::TYPE_DCVS_FLEX_UPDATED => "Flexible Variables Updated",
            self::TYPE_DCVS_GLOBAL_UPDATED => "Global Variables Updated"
        ),

        // Video Administration
        array( self::CAT_VIDEO_ADMIN => "Video Administration" ) => array(
            self::TYPE_VIDEO_ADDED => "Video Added",
            self::TYPE_VIDEO_EDITED => "Video Edited",
            self::TYPE_VIDEO_REMOVED => "Video Removed"
        ),

        // Bulletin Board Administration
        array( self::CAT_BULLETIN_BOARD => "Bulletin Board Administration" ) => array(
            self::TYPE_BULLETIN_DELETED => "Message Deleted",
            self::TYPE_BULLETIN_EDITED => "Message Edited",
            self::TYPE_BULLETIN_ADDED => "Message Added"
        ),

        // User Administration
        array( self::CAT_USER_ADMIN => "User Administration" ) => array(
            self::TYPE_USER_ADDED => "User Added",
            self::TYPE_USER_ADDED_MULTI => "Multiple Users Added",
            self::TYPE_USER_REMOVED => "User Removed",
            self::TYPE_USER_REMOVED_MULTI => "Multiple Users Removed",
            self::TYPE_USER_UPDATED => "User Updated"
        ),

        // Survey Administration
        array( self::CAT_SURVEY_ADMIN => "Survey Administration" ) => array(
            self::TYPE_SURVEY_ADDED => "Survey Added",
            self::TYPE_SURVEY_UPDATED => "Survey Updated",
            self::TYPE_SURVEY_REMOVED => "Survey Removed",
            self::TYPE_SURVEY_REMOVED_MULTI => "Multiple Surveys Removed"
        )
    );

it's kind of annoying to make another array just to define what is being defined in the keys here, so i was wondering if that was my problem. if it is, i guess i'll have to make a key-value array for the categories ids and string values.

thanks!

Answer 1

You're getting an illegal offset type error because array keys can only be scalar values. From the documentation on arrays:

A key may be either an integer or a string. If a key is the standard representation of an integer, it will be interpreted as such (i.e. "8" will be interpreted as 8, while "08" will be interpreted as "08"). Floats in key are truncated to integer.

Since self::CAT_CRON_JOBS et al. seem like they should be constants anyways, why not just define them so that their value is the description text, and then you could just specify your array like

const CAT_STATEMENT_ADMIN = "Document Administration";

public static $CATS_AND_TYPES = array(

  // Statement Administration
  self::CAT_STATEMENT_ADMIN => array(
    self::TYPE_STATEMENTS_LOADED => "Documents Loaded",
    self::TYPE_STATEMENTS_REMOVED => "Documents Removed"
  ),

  // etc.
)

And then you could use either $CATS_AND_TYPES[self::CAT_STATEMENT_ADMIN] (within the class, of course) or $CATS_AND_TYPES['Document Administration'] to get the same array element.

Answer 2

No. Arrays can only have integers and strings as keys.

You can simulate arrays and use objects as keys with SplObjectStorage. No arrays, though.

Answer 3

I think it's your problem :P

I would approach the problem like this

public static $CATS_AND_TYPES = array(

    self::CAT_STATEMENT_ADMIN => array(
        self::TYPE_STATEMENTS_LOADED,
        self::TYPE_STATEMENTS_REMOVED
    ),

    // ...
);

public static $TRANSLATIONS = array(
    self::CAT_STATEMENT_ADMIN => 'Email Administration',
    self::TYPE_STATEMENTS_LOADED = "Documents Loaded",
// ...

I guess that's basically what you meant by "make another array." This is the correct approach to the problem because it separates translation and the hierarchical information.

Imagine when you want to translate your project to another language. If you hired a translator, he shouldn't need to know your project's hierarchical structure because he should only translate. You can also extract $TRANSLATIONS into another file so that you can distribute that file to 99 translators and your project will be multilingual in one day!

If you are so inclined, you can serialize your array into a scalar value so it can act as a key.

// Untested
public static $CATS_AND_TYPES = array(
    serialize(array(self::CAT_STATEMENT_ADMIN=>"Documents and Administration")) => array(
        self::TYPE_STATEMENTS_LOADED => "Documents Loaded"
        // ...
    )
);

// You can later get back the values
foreach(self::CATS_AND_TYPES as $k=>$v)
{
    $title = unserialize($k);
    displayTitle($title[0]);

    foreacH($v as $bar) displaySubtitle($bar);
}