Hi internals, In PHP, variables are currently scoped to the function scope, and can't be scoped to a block scope. This makes it difficult to reason about how a variable will actually be used at a glance, especially in long functions, or top-level statement lists of a file. (or how the variable was originally intended to be used)
The function scope lifetime of variables in PHP is similar to how JavaScript treated variables with `var`, before the introduction of the `let` statement in JS: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/let Would there be any interest in adding something similar to this in PHP? (Or have similar ideas been proposed in the past? I didn't see any.) Correctness would be enforced as a best-effort at compile-time - the variables would continue to only be freed at the end of the function call. (e.g. __destruct() only gets called when the variable gets reassigned or the function call ends) - Freeing it immediately would likely require the equivalent of a try{} finally{} to handle exceptions. try statements prevent opcache from optimizing a function, the last time I checked. ``` { let $myObject = new MyClass(), $flag = true; $myObject->process($flag); } // Accessing or setting $myObject or $flag outside a different let is an E_COMPILE_ERROR // because it was declared anywhere else in the function body // as a let statement $myObject->doSomething(); // E_COMPILE_ERROR to access $key or $value after, outside of a separate `let` scope foreach ($arr as let $key => let $value) { // It would be a compile error to declare a gotoLabel: inside of a scope of a let statement. } // E_COMPILE_ERROR to access $key or $value after echo $$var; // E_COMPILE_ERROR to use variable variables in the same scope, to enforce this as much as possible. { let $outer = 1; { let $outer = 2; // E_COMPILE_ERROR to declare in a different scope, can only reassign $outer = 3; // this is allowed } } { let $myRef =&$other; } { let $myRef = true; // This removes myRef from the reference group before assigning a new value to myRef - $other is unmodified. } ``` I say "best-effort" because require() and $GLOBALS and get_defined_variables() can still read or modify or make references to variables outside of a `let`, depending on what's in the function body or top-level statements. - Tyson -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
