php null coalescing operator in combination with concatenation operator does not work right

Question

This code echo "2" instead of "2some text"!

$x = 2;
echo $x??0 . "some text";

If we put the $x??0 in parentheses, the result is correct:

$x = 2;
echo ($x??0) . "some text";

now result is: 2some text

Is something wrong in the above code or is a php bug?

No need to concatenate output with echo using a .. You can use a , (comma) instead. — Markus Zeller
– Markus Zeller, Commented Nov 6, 2019 at 16:56

Alex Howansky · Accepted Answer · 2019-11-06 16:02:59Z

4

This is the correct behavior. The string concatenation . operator has higher precedence than the null coalesce operator ??, so (as you've noted) you need to use parens to force the desired behavior. Without parens, the code is interpreted as if you had done this:

echo $x ?? (0 . "some text");

See here for details.

answered Nov 6, 2019 at 16:02

Alex Howansky

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1 Comment

treyBake Over a year ago

may be worth noting that without the brackets around the $x??0 - it's comparing 2 vs 0.some Text - which of course renders 2 because $x is not null

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