What's the difference between these two sentences?

$arr = $db->getrows ("SELECT * from Pinglun");

What's the difference between these two?
foreach ($arr as $k = = $v) {

foreach ($arr as $v) {

I see the output is the same.

Why do you want to add a =

Reply to discussion (solution)

Two sentences are the same, just
foreach ($arr as $k = = $v) {
You can read array subscript with $k
foreach ($arr as $v) {
This sentence is not

If you only care about values, the same

If you still care about key, it is different, many times we need to deal with the value of close-up key alone need to use $k=> $v

If you don't have to $k, then it's the same.

Process is the same as whether you need to get the array key

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