Symfony 4: Var-dumper not working properly

Question

I tried to use the wonderful dump function from the var-dumper bundle in symfony 4 and for some reason I get the following error:

Failed to start the session because headers have already been sent by "vendor\symfony\var-dumper\Dumper\AbstractDumper.php" at line 181.

Additionally, when I try to use the {% dump foo %} tag in a twig template I get an error:

Unknown "dump" tag.

Can anyone help me?

Answer 1

A guy named Simon Waldburger mentioned in the lesson's comments that installing "debug" fixed the issue (it fixed it for me). The instruction was in the next lesson.

composer require debug --dev

iiirxs is also correct, to output dump in twig file, do

{{ dump(variable) }}