PHP best way of unsetting a variable

Question

$num = 1;    
$var = ''

if ($num == 1) {
  $var = 'ONE';
}

if (isset($var)) {
  echo $var;
}

// Result: ONE

In the above example, which is best practice when checking against isset()?

$var = '';

or

$var = null;

It would probably help if you explained what you're trying to achieve. — jcuenod, Aug 11 '15 at 21:52
@jcuenod I assume he wants to keep `$var` in the scope of the rest of the code and wants to make it outside of the `if statement` but isn't sure how to define it. — Script47, Aug 11 '15 at 21:53
possible duplicate of [What's better at freeing memory with PHP: unset() or $var = null](http://stackoverflow.com/questions/584960/whats-better-at-freeing-memory-with-php-unset-or-var-null) — Deenadhayalan Manoharan, Aug 12 '15 at 06:49

score 2 · Answer 1 · answered Aug 11 '15 at 21:50

2

It kind of depends more broadly on what you're trying to do.
I'm not convinced unsetting a variable is your best bet here.

However, PHP does have an unset function:

unset($var);

To be clear, I agree that checking for emptiness is probably a better idea

answered Aug 11 '15 at 21:50

jcuenod

Especially when using references `unset()` has to be used. – Erik Theoboldt Aug 11 '15 at 21:53

score 1 · Accepted Answer · answered Aug 11 '15 at 21:47

By setting $var = ''; near the top, isset will return true every time. What you want, is to check if the $var is empty.

Change:

if (isset($var)) {
  echo $var;
}

to

if (!empty($var)) {
  echo $var;
}

Otherwise, simply remove the original $var = ''; near the top and you can continue to use isset.

2 Answers2