Adding variables in PHP 8.2 heredoc not working

Question

I'm using PHP 8.2. I have the following heredoc:

$a = 4; 
$b = 2;

$str = <<<EOT
$a + $b = {$a + $b}
EOT;

print $str;

Error:

PHP Parse error: syntax error, unexpected token "+", expecting "->" or "?->" or "["

The error is happening on the + sign inside the curly-braces {$a + $b}. I'm reading that complex variable interpolation is a bit different in PHP 8.2, but I cannot find any examples of how to do math with PHP variables inside a heredoc.

What am I missing?

Robert · Accepted Answer · 2025-10-25 18:29:58Z

1

Advanced string interpolation allows to execute arbitrary code in substitutions, like calling member functions, e.g., ${$myObject->someFunction()}. So you could move the logic into functions and use those. That would also make them easy to test.

Looks like there was a RFC to extend string interpolations but it didn't go anywhere.

answered Oct 25 at 18:29

Robert

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1 Comment

John Cowan Oct 25 at 19:31

Thanks for your post. It pointed me in the right direction to -- begin understanding this.

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