Static keyword doesn't work inside PHP generator function - php

Question

It seems that the static keyword does not work inside generator functions?
In PHP 5.5:
function static_fn () {
static $p = 0;
echo "\nstatic_fn: p = " . $p . "\n" ;
$p++;
}
echo "calling static_fn()\n";
static_fn();
echo "calling static_fn()\n";
static_fn();
function static_gen() {
static $p = 0;
echo "\nstatic_gen: p = " . $p . "\n" ;
yield $p;
}
echo "calling static_gen()\n";
foreach(static_gen() as $stuff) {
echo $stuff . "\n";
}
echo "calling static_gen()\n";
foreach(static_gen() as $stuff) {
echo $stuff . "\n";
}
I get the result
calling static_fn()
static_fn: p = 0
calling static_fn()
static_fn: p = 1
calling static_gen()
static_gen: p = 0
0
calling static_gen()
static_gen: p = 0
0
That is, the static keyword worked successfully for the static_fn function which returned 0 and 1 from consecutive calls, but it did not work for the static_gen function where it was reinitialised to 0 in each call.
Does anyone know why this is so, and how one might work around it to replicate static variables in a generator?

Answer 1

Try this:
function static_gen() {
static $p = 0; #initialised
while ($p < 10) { #yield while $p is smaller than 10
$p++; #increased
echo "\nstatic_gen: p = " . $p . "\n" ;
yield $p; #yield value
}
}
That will work.
Sidenote: A generator function must yield values as long as values are given. So the function must provide it in one or a other way.

Answer 2

Just like #JustOnUnderMillions have commented above, static vars aren't shared among functions.
Static variables has scope per function.
Moreover, generators is not aimed to do what you've did (okay, maybe you are just testing something :)).
Anyway you could change you static_gen() to:
function static_gen()
{
static $p = 0;
echo "\nstatic_gen: p = " . $p . "\n";
yield $p++;
}
But again, it's is so weird.