非严格的平等比较

Question

Today I was exploring the symfony repo and found some pull requests by @Seldaek where he switched the variable with the value as you can see bellow:

Link for the PR

What's the difference between having $var === true and true === $var?

Answer 1

There is no functional difference, it's a coding style called yoda conditions.

People use it to avoid accidental assignments in conditions which normally wouldn't be picked up by the compiler when the constant is second.

This is a valid statement, and will be difficult to debug when actually expected it to perform a comparison:

if ($var = 12) {}

This is an invalid statement and will throw an error

if (12 = $var) {}

as we cannot assign the variable to 12.