Why does PHP not complain when I treat a null value as an array like this?

Question

In PHP, I have error_reporting set to report everything including notices.

Why does the following not throw any notices, errors or anything else?

$myarray = null; $myvalue = $myarray['banana']; 

Troubleshooting steps:

$myarray = array(); $myvalue = $myarray['banana']; // throws a notice, as expected ✔  $myarray = (array)null; $myvalue = $myarray['banana']; // throws a notice, as expected ✔  $myarray = null; $myvalue = $myarray['banana']; // no notice or warning thrown, $myvalue is now NULL. ✘ Why? 

It's possible it's a bug in PHP, or I'm just not understanding something about how this works.

Answer 1

There are three types which it might be valid to use the array derefence syntax on:

• Arrays
• Strings (to access the character at the given position)
• Object (objects implementing the ArrayAccess interface)

For all other types, PHP just returns the undefined variable.

Array dereference is handled by the FETCH_DIM_R opcode, which uses zend_fetch_dimension_address_read() to fetch the element.

As you can see, there is a special case for NULLs, and a default case, both returning the undefined variable.