Edit report at http://bugs.php.net/bug.php?id=54039&edit=1
ID: 54039
User updated by: a at b dot c dot de
Reported by: a at b dot c dot de
Summary: use() of static variables in lambda functions can
break staticness
Status: Open
Type: Bug
Package: Scripting Engine problem
Operating System: Windows XP
PHP Version: 5.3.5
Block user comment: N
Private report: N
New Comment:
A little further testing gives this:
function test_1()
{
static $v = '';
$v .= 'b';
echo "Outer function catenates 'b' onto \$v to give $v\n";
$f = function()use($v)
{
echo "Inner function reckons \$v is $v\n";
};
$v .= 'a';
echo "Outer function catenates 'a' onto \$v to give $v\n";
return $f;
}
$f = test_1(); $f();
$f = test_1(); $f();
$f = test_1(); $f();
$f = test_1(); $f();
The second concatenation ('a') fails to be retained; if only the
anonymous function didn't use($v), the variable would end up containing
'babababa'.
Previous Comments:
------------------------------------------------------------------------
[2011-02-18 00:49:00] a at b dot c dot de
Description:
------------
Let an ordinary function declare a static local variable, and let it
also define an anonymous function that uses that static variable. It can
happen that the static variable no longer retains its value across calls
to the ordinary function; i.e., it loses that static property.
It seems to be limited to situations where the anonymous function is
defined before the static variable has had its value changed.
Test script:
---------------
function test_1()
{
static $v = 0;
++$v;
echo "Outer function increments \$v to $v\n";
$f = function()use($v)
{
echo "Inner function reckons \$v is $v\n";
};
return $f;
}
echo "\nIncrement static variable, then use it in anonymous function
definition:\n";
$f = test_1(); $f();
$f = test_1(); $f();
function test_2()
{
static $v = 0;
$f = function()use($v)
{
echo "Inner function reckons \$v is $v\n";
};
++$v;
echo "Outer function increments \$v to $v\n";
return $f;
}
echo "\nUse static variable in anonymous function definition, then
increment it:\n";
$f = test_2(); $f();
$f = test_2(); $f();
Expected result:
----------------
Increment static variable, then use it in anonymous function
definition:
Outer function increments $v to 1
Inner function reckons $v is 1
Outer function increments $v to 2
Inner function reckons $v is 2
Use static variable in anonymous function definition, then increment
it:
Outer function increments $v to 1
Inner function reckons $v is 0
Outer function increments $v to 2
Inner function reckons $v is 1
Actual result:
--------------
Increment static variable, then use it in anonymous function
definition:
Outer function increments $v to 1
Inner function reckons $v is 1
Outer function increments $v to 2
Inner function reckons $v is 2
Use static variable in anonymous function definition, then increment
it:
Outer function increments $v to 1
Inner function reckons $v is 0
Outer function increments $v to 1
Inner function reckons $v is 0
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/bug.php?id=54039&edit=1
