Unfortunately they are becoming more and more prevalent in the PHP community. For example, here they are in the Symfony project's coding standards: http://symfony.com/doc/current/contributing/code/standards.h...

The rationale is that they make it a compiler error if you accidentally perform an assignment operation ("xyz" = $name) instead of a comparison ("xyz" === $name). The thing is, this is only a significant risk if you adopt the bad habit of performing assignment operations within conditional statements, like this:

    if (null !== ($charset = $env->getCharset())) {

The above style has been popularised in PHP by the Symfony project. I think it's hideous, and that the idea of adopting one ugly style choice (Yoda Expressions) to mitigate the risk introduced by another ugly style choice (assignment in conditional operations) is reminiscent of the children's song about the old lady who swallowed a fly.