Why Does PHP Speak Hebrew?

This is my first post on a PHP topic, where I’ll talk about something very unusual that I saw while working on a PHP script. At first it seems like a minor find, but on digging further it turned out to be a small window into the history and politics of the development of PHP language. While checking whether a variable is empty before using it in a function, I did this:

if (isset($a)) {
 // do something
}

Then I wanted to see what happens when $a is null:

if (isset(null)) {
 // do something
}

This gave me an error message that I’ve never seen before: Parse error: syntax error, unexpected ')', expecting T_PAAMAYIM_NEKUDOTAYIM The location of the error was on the line containing if (isset(null)).

The same message came up when I used empty(null) instead of isset(null).

This error message seemed like gibberish, but having studied Hebrew for a few months back in high school, I could tell that this gibberish looked suspiciously like Hebrew! A quick search showed that this was indeed Hebrew. “Paamayim nekudotayim” means “double colon” (::) in Hebrew. This begs two questions. First, why was PHP looking for a double colon here? And second, why was the error message in Hebrew?

The first question seems easier to answer. In the PHP manual, the empty() function is described like this:

bool empty ( mixed $var )

In other words, this function requires a variable as a parameter. Since null was not prefaced with a $, PHP interpreted it as a class name and continued to look for a variable. Since a variable that’s prefaced by a class name has to be a static variable in that class, PHP looked for ::, the static separator.

The question of why the message is in Hebrew opens a little window into the history of PHP. It turns out that the compilers for PHP 3 and PHP 4 were developed in Israel by Andi Gutmans and Zeev Suraski. The PHP 4 compiler was called Zend Engine and increasingly more advanced versions of it went on to power all versions of PHP since 4. The Hebrew name of the double colon was inserted as an easter egg by the developers as a reminder of PHP’s origin. This has been a controversial topic in the PHP community, as described in detail on Phil Sturgeon’s blog. On one hand, the “conservative” faction wanted to keep the Hebrew name to preserve the history of PHP. On the other hand, the “progressive” faction was sympathetic with the annoyed and puzzled developers googling “paamayim nekudotayim”, and keenly aware of the hundreds (or thousands?) of hours of time collectively wasted on such googling.

Over time, the “progressive” faction became dominant, but as with most issues related to politics, change happened slowly. PHP Sandbox allowed me to trace the evolution of “paamayim nekudotayim” error message through different versions of PHP. I noticed this mysterious error message while using PHP 5.3. This was lucky because 5.3 was the last version where this error stated “expecting T_PAAMAYIM_NEKUDOTAYIM”. In PHP 5.4, the error text was changed to

syntax error, unexpected ')', expecting :: (T_PAAMAYIM_NEKUDOTAYIM)

The mention of the double colon was helpful, but the mysterious paamayim nekudotayim was still there spreading confusion, and the error message was still not more helpful with figuring out why PHP was looking for a double colon here. In PHP 5.5, the error changed to

Cannot use isset() on the result of an expression (you can use "null !== expression" instead)

This is a much better error message. Not using isset() on the result of an expression makes more sense than not looking for a double colon. In PHP 7, the error message changed again to

Cannot use 'null' as class name as it is reserved

Here, PHP returns to considering any function arguments that are not prefaced with “$” as class names, but it states so explicitly, so that we don’t have to seek help from our friendly neighborhood PAAMAYIM NEKUDOTAYIM to figure this out.