为什么这个数组元素的值解析为零？

Question

I'm working on pagination for my website, yet I'm stuck on the following piece of code. I've been messing around with it for at least an hour, and can't seem to wrap my head around what's going on with the output.

Of course the if statement executes once.

And as expected the first echo ... returns 1.

However, for some reason the second echo ... returns 0 as a float instead of <div>1</div> as a string...

$rowCount = 5;

$pgCount = ceil($rowCount / 10);

$pgParamArray["page"] = $pgCount;

$pgArray = array("", "", "", "", "");

for ($i = 0; $i < 5; $i++) {

  if ($pgParamArray["page"] - $i > 0) {

    echo $pgParamArray["page"] - $i;

    $pgArray[$i] = "<div>" . $pgParamArray["page"] - $i . "</div>";

    echo $pgArray[$i];

  }

}

• I have tried setting $pgArray as array() and array($v1, $v2, $v3, $v4, $5) with no luck.

• Even though var_dump($pgParamArray) returns float, I tried converting $rowCount, which is initially a string from the database, to a number anyways. No dice again.

• echo $pgArray["0"] also returns 0.

• var_dump($pgArray[0]) also returns float.

• var_dump($pgArray) obviously returns array.

• However, var_dump($pgArray) returns array(5) { [0]=> string(7) ...

I have absolutely zero idea why $pgArray[0] returns 0, yet var_dump($pgArray) returns array(5) { [0]=> string(7) .... That makes zero sense to me. Anybody know why $pgArray[0] is resolving to 0?

Answer 1

Wrapping your statement in parenthesis seems to work for me:

$pgArray[$i] = "<div>" . ($pgParamArray["page"] - $i) . "</div>";

Without the parenthesis, it seems that the value breaks completely; the page doesn't print the <div> tags at all, but rather just adds a trailing 0 to the already printed 1.

I would assume that it's due to how PHP processes string concatenation, though I wouldn't be able to give you an exact answer as to why this happens. Just to be safe, I'd always either store any equations in variables before you pass them in, or perform all operations inside of parenthesis.

That way, you won't have weird encounters like this (for example):

echo "<div>" . 1 + 1 . "</div>";     // returns 1
echo "<div>" . (1 + 1) . "</div>";   // returns 2