Unset all variables in PHP 7

Question

I'm using the following script in PHP 5.5.9 to unset all variables, which works great

$vars = array_keys(get_defined_vars());
for ($i = 0; $i < sizeOf($vars); $i++) {
    unset($$vars[$i]);  //this is line 72
}
unset($vars,$i);

However, in PHP 7, they give the following messages:

PHP Notice:  Array to string conversion in /root/script.php on line 72
PHP Notice:  Undefined variable: Array in /root/script.php on line 72

My question is how to make the script work in PHP 7?

Thanks for any suggestion!

Answer 1

You can avoid those errors by using foreach instead of for.

$vars = array_keys(get_defined_vars());
foreach ($vars as $var) {
    unset($$var);
}
unset($vars, $var);

The order of evaluation of $$vars[$i] is different in PHP 7. It's now strictly left to right.

Previously it would have first evaluated $vars[$i] and then formed a new variable from the result of that with $.

Now it first evaluates $$vars and then tries to find [$i] in the result of that.