Use of increment operator in heredoc

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I want to increase the value of a variable by using the increment operator in heredoc. My current code is given below...

$counter = 0;
for($i = 0; $i<10; $i++):
echo <<< EOT
    $counter++ <br/>
EOT;
endfor;

Its output is...

0++
0++
.
.

Mean post-increment operator is not working.

I have also tried pre-increment, like given below...

echo <<< EOT
   ++$counter <br/>
EOT;

Its output is...

++0
++0
.
.

Mean pre-increment operator is also not working.

I have also tried to put increment operation inside curly braces, like given below...

echo <<< EOT
    {++$counter} <br/>
EOT;

But again no luck. Output is....

{++0} 
{++0} 
.
.

I have also searched it on google but didn't find anything useful.

I know if I can increase value before heredoc then I can print it in here doc correctly

$counter = 0;
for($i = 0; $i<10; $i++):
++$counter;
echo <<< EOT
    $counter <br/>
EOT;
endfor;

It works fine.

But I want to use increment operator in heredoc, just like we use in case of single or double quoted with echo.

But it seems like heredoc doesn't support increment operation.

heredoc php
1 Answers

The complex/curly variable syntax {$var…} does only allow variable access expressions, but not PHP expressions per se.

  • For example {$var[…]}
  • Or {$var(…)}
  • And {$var->prop…}
  • And {${stat::$lookup}}

There can't be arithmetic operators within the { + } itself. But only between […] or (…) used alongside.

*

One common workaround is to utilize variable function names:

$func = "htmlspecialchars";  // or any other no-op function
echo <<<HEREDOC
    counter = {$func($counter++)}
HEREDOC;

Where you can easily use full expressions in the curly var syntax.

user_3450310
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