====== PHP RFC: Isset/Set Operator ======
  * Version: 0.1
  * Date: 2013-11-24
  * Author: Chris London, me chrislondon co
  * Status: Draft (Inactive)

===== Introduction =====

Two new operators. ?= for setting the value of an unset or falsey variable. And ??: which acts like ?: except it it also checks is set.

===== Proposal =====

?= Will be a new operator that allows the user to set an unset or falsey variable. This handy operator will help avoid dreaded unset variable notices.

    $foo ?= 'default';
    
    // which is functionally equivalent to:
    $foo = (isset($foo) && $foo) ? $foo : 'default';
    
    // or
    if (!isset($foo) || !$foo) $foo = 'default';

??: will be equivalent to the ternary short hand ?: except that it also checks for isset().

    // $bar is unset
    
    $foo = $bar ?: 'other'; // Throws undefined notice
    
    $foo = $bar ??: 'other'; // Does NOT throw undefined notice
    
    // ??: is functionally equivalent to:
    $foo = (isset($bar) && $foo) ? $bar : $other;
    
This will be very helpful for echoing default variables in HTML like so:

    <div class="<?= $user ??: 'guest' ?>"> ... </div>

===== Backward Incompatible Changes =====

Nothing yet.

===== Proposed PHP Version(s) =====

Next PHP 5.x

===== SAPIs Impacted =====

Not yet known.

===== Open Issues =====

**Possible Alternatives To ?= Operator**

  - ?:=
  - ||=
  - @=

**Possible Alternatives To ??: Operator**

  - ?::
  - ?: (backward compatibility concerns)
  - || (backward compatibility concerns)
  - @:

===== Unaffected PHP Functionality =====



===== Future Scope =====

This sections details areas where the feature might be improved in future, but that are not currently proposed in this RFC.

===== Proposed Voting Choices =====

Include these so readers know where you are heading and can discuss the proposed voting options.

===== Patches and Tests =====

Links to any external patches and tests go here.

If there is no patch, make it clear who will create a patch, or whether a volunteer to help with implementation is needed.

Make it clear if the patch is intended to be the final patch, or is just a prototype.

===== Implementation =====

After the project is implemented, this section should contain 
  - the version(s) it was merged to
  - a link to the git commit(s)
  - a link to the PHP manual entry for the feature

===== References =====

Links to external references, discussions or RFCs

===== Rejected Features =====

Keep this updated with features that were discussed on the mail lists.