Assign and use variable inside of PHP if statement

Question

I am wondering whether it is possible to use a variable inside of the same if statement that it is assigned in using PHP.

For example:

if ($start = strtotime($_POST['date']) && $start <= time()) {
    $error = 'You must choose a date in the future.';
}

That code does not appear to be working for me, but I don't see why it shouldn't since I know the variable can be assigned like that, and it would make sense for me for the following variable to then be able to access it.

Possible duplicate of Set variable in if statement expression — JDSchenck
– JDSchenck, Commented Feb 13, 2018 at 5:04
@JDSchenck that thread does not address whether or not I can use the assigned variable in the same statement — Goulash
– Goulash, Commented Feb 13, 2018 at 5:06
@Barmer, when i post a date in the future, the statement returns "You must choose...". Please see eval.in/955103. — Goulash
– Goulash, Commented Feb 13, 2018 at 5:07

Barmar · Accepted Answer · 2018-02-13 05:08:59Z

8

You're running into operator precedence problems. && has higher precedence than =, so it's being processed as:

if ($start = (strtotime($_POST['date']) && $start <= time())) {

This doesn't assign to $start until after the && expression completes, which means it will try to use $start in the comparison before it has been assigned. And it also assigns a boolean true/false value to $start, which is obviously not useful.

Either put parentheses around the assignment, or use the lower precedence and operator:

if (($start = strtotime($_POST['date'])) && $start <= time()) {

if ($start = strtotime($_POST['date']) and $start <= time()) {

answered Feb 13, 2018 at 5:08

Barmar

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1 Comment

Goulash Over a year ago

@AlivetoDie This answer addressed the problem exactly. The problem was the higher order of &&, if you want to see an example of the problem, see here: eval.in/955110.

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