accessing value of next() and rewind() in a PHP iterator run in a foreach loop
Saw this in wikipedia, this is what happens when you traverse an iterator via a foreach loop:
These methods are all being used in a complete foreach( $object as $key=>$value ) sequence. The methods are executed in the following order:
rewind()
while valid() {
current() in $value
key() in $key
next()
}
End of Loop
I was wondering how I ca开发者_运维知识库n access the values of next() and rewind(). Any ideas?
UPDATE: Access them from inside the foreach loop
What do you think about it?
for ($i =0; $i < count($arr); $i++) {
$last = ($i == 0) ? null : $arr[$i-1];
$next = (isset($arr[$i+1]) ? $arr[$i+1] : null;
$current = $arr[$i];
//...
}
You can't. To trigger a reset
, you'd need to reenter the loop, and to call next
, you need to go into the next iteration.
So the closest (PHP 5.3) would be this:
label:
foreach ($var as $k => $v) {
/* ... */
goto label; //re-enter loop
/* ... */
continue; //force going to the next iteration
/* ... */
}
If you are using iterators directly, you can use those calls:
$r = 0; $s = 0;
$it = new ArrayIterator(array("a" => 3, "b" => 5, "c" => 7));
foreach ($it as $k => $v) {
echo "$k => $v\n";
if ($s == 0) {
$s = 1;
$it->next(); //jump over one iteration
} else if ($r == 0) {
$r = 1;
$it->rewind();
}
}
gives:
a => 3 c => 7 b => 5 c => 7
IF its implementing the Iterator
interface you can call those method yourself but they have implications.
rewind
and next
both set the position of the pointer in the dataset being iterated over... they dont actually return the element or index. So calling either of these is going to screw up your loop.
current
will return the same variable you already have in the loop - ie. the element for the current iteration. key
will return the index for that item in the set.
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