Ampersand before the variable in foreach loop

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Reference - What does this symbol mean in PHP?

I need to know why we use ampersand before the variable in foreach loop

foreach ($wishdets as $wishes => &$wishesarray) {
    foreach ($wishesarray as $categories => &$categoriesarray) {

    }
}

Thanks

---

This example will show you the difference

$array = array(1, 2);
foreach ($array as $value) {
    $value++;
}
print_r($array); // 1, 2 because we iterated over copy of value

foreach ($array as &$value) {
    $value++;
}
print_r($array); // 2, 3 because we iterated over references to actual values of array

Check out the PHP docs for this here: http://pl.php.net/manual/en/control-structures.foreach.php

---

This means it is passed by reference instead of value... IE any manipulation of the variable will affect the original. This differs to value where any modifications don't affect the original object.

This is asked many times on stackoverflow.

---

It is used to apply changes in single instance of array to main array..

As:

//Now the changes wont affect array $wishesarray

foreach ($wishesarray as $id => $categoriy) {
      $categoriy++;
}
print_r($wishesarray); //It'll same as before..

But Now changes will reflect in array $wishesarray also

foreach ($wishesarray as $id => &$categoriy) {
      $categoriy++;
}
print_r($wishesarray); //It'll have values all increased by one..

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