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Thread-Topic: PHP5x question related to opcode caching & HashTable entries
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Date: Tue, 16 Feb 2016 21:13:51 +0000
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Subject: PHP5x question related to opcode caching & HashTable entries
From: ericsten@microsoft.com (Eric Stenson)

Internals Folks--

I'm investigating a problem in WinCache's opcode caching for PHP5x, and I'm=
 baffled. =20

Could someone please explain the difference between the two following code =
fragments?  Specifically, what is the difference in the HashTable and Bucke=
t entries in C.

/* Assume $values is an empty array, and $defaults is populated via Reflect=
ionClass::getDefaultProperties(), and definitely contains an element 'Banan=
a'=3D>'some string' */

Fragment 1:
    foreach ($defaults as $key =3D> $value) {
      $values["${key}"] =3D $value;  /* <--- this line */
    }
    var_dump(isset($values['Banana']));

Fragment 2:
    foreach ($defaults as $key =3D> $value) {
      $values[$key] =3D $value;      /* <--- this line */
    }
    var_dump(isset($values['Banana']));


For scripts cached in WinCache, Fragment 1 works, but Fragment 2 doesn't wo=
rk.  I've single-stepped thru zend_isset_isempty_dim_prop_obj_handler_SPEC_=
VAR_CONST() in the debugger, both cached and un-cached, and it appears that=
 the Bucket->h value is incorrect in the Fragment 2 case.

WinCache's opcode caching code looks like it can't get this wrong; It shoul=
d be faithfully copying the Bucket->h value whenever it caches the opcode a=
rray.

Any help in understanding the difference in what the Zend Core does with th=
e two fragments would be very helpful!

Thx!
    --E.