Why this line of code does not work in php like as in JS:
$id = [];
$id = null || [];
if (count($id)) {
echo 'd';
}
Why $id still is null instead empty array []? Therefore count() gives an error.
3 Answers
In PHP, logical operators like || always return a boolean, even if given a non-boolean output.
So your statement is evaluated as "is either null or [] truthy?" Since both null and an empty array evaluate to false, the result is boolean false.
There are however two operators which would do something similar to JS's ||:
$a ?: $bis short-hand for$a ? $a : $b; in other words, it evaluates to$aif it's "truthy", or$bif not (this is documented along with the ternary operator for which it is a short-hand)$a ?? $bis similar, but checks fornullrather than "truthiness"; it's equivalent toisset($a) ? $a : $b(this is called the null-coalescing operator)
Comments
<?php
// PHP < 7
$id = isset($id) ? $id : [];
// PHP >= 7
$id = $id ?? [];
// PHP >= 7.4
$id ??= [];
As of PHP 7 and above
Null Coalesce Operator
Another helpful link
Comments
Watch out!
I find PHP's handling of empty to be highly questionable:
empty($unsetVar)== true (fabulous, no need to checkissetas warning is suppressed!)empty(null)== trueempty('')== true
All fine, until we get to this nonsense:
empty(false)== true. Wait, WHAT???
You've GOT to be kidding me. In no world should false be taken to mean the same thing as no value at all! There's nothing "empty" about a false assertion. And due to this logical fallacy, you cannot use empty to check ANY variable that might have a VALUE of false.
In my projects, I use a static method:
public static function hasValue($value) {
return isset($value) && !is_null($value) && $value !== '';
}
Of course, using this method, I no longer get the free warning suppression provided by empty, so now I'm also forced to remember to call the method above with the notice/warning suppression operator @:
if(self::hasValue(@$possiblyUnsetVar)) {}
Very frustrating.
$id = null ?? [];???$idis assignedfalsenotnull. See also: stackoverflow.com/questions/15327508/why-countfalse-return-1