Add chapter about increment/decrement operators

wordpress-coding-standards/php.md

@@ -600,6 +600,26 @@ While this operator does exist in Core, it is often used lazily instead of doing
 
 > Warning: Prior to PHP 8.0.0, it was possible for the @ operator to disable critical errors that will terminate script execution. For example, prepending @ to a call of a function that did not exist, by being unavailable or mistyped, would cause the script to terminate with no indication as to why.
 
+### Increment/decrement operators
+
+When writing increment (`++`) or decrement (`--`) operators, there should be no spaces between the operator and the variable it applies to. Pre-increment/decrement should be favoured over post-increment/decrement for stand-alone statements.
+
+Pre-increment/decrement will increment/decrement and then return, while post-increment/decrement will return and then increment/decrement.
+Using the "pre" version is slightly more performant and can prevent future bugs when code gets moved around.
+
+```php
+// Correct.
+for ( $i = 0; $i < 10; $i++ ) {}
+
+--$a;
+
+// Incorrect.
+for ( $i = 0; $i < 10; $i ++ ) {}
+
+$a--;
+++   $b; // Multiple spaces.
+```
+
 ## Database
 
 ### Database Queries