如何使用PHP将零值视为真？

Question

Here is my sample code:

$issue_id = $_POST['issue_id'];
if(!empty($issue_id)){
  echo 'true';
}
else{
   echo 'false';
}

If I pass 0 to $_POST['issue_id'] by form submitting then it echo false. Which I want is: Condition will be true if the following conditions are fulfilled: 1. true when I pass any value having 0. 2. false when I don't pass any value. i.e: $_POST['issue_id'] is undefined.

I also tried this:

if(!isset($issue_id)){
  echo 'true';
}
else{
   echo 'false';
}


if(!empty($issue_id) || $issue==0){
  echo 'true';
}
else{
   echo 'false';
}

The last one is okay, meaning if I pass any value having ZERO then it will echo true. But it will also echo true if I don't pass any value. Any idea?

Answer 1

The last is okay, meaning if I pass any value having ZERO then it echo true. But it also echo true if I don't pass any value. Any idea?

if (isset($_POST["issue_id"]) && $_POST["issue_id"] !== "") {
}

please notice I used !== not !=. this is why:

0 == "" // true
0 === "" // false

See more at http://php.net/manual/en/language.operators.comparison.php

---

also if you are expecting number you can use

if (isset($_POST["issue_id"]) && is_numeric($_POST["issue_id"])) {
}

since is_numeric("") returns false

http://php.net/manual/en/function.is-numeric.php

---

Alternatively if you expect number good option is filter_var

if (isset($_POST["issue_id"]) {
   $issue_id = filter_var($_POST["issue_id"], FILTER_VALIDATE_INT);
   if ($issue_id !== false) { 
   }
}

since filter_var("", FILTER_VALIDATE_INT) will returns false and filter_var("0", FILTER_VALIDATE_INT) will return (int) 0

http://php.net/manual/en/function.filter-var.php