Pretty printer generates least-parentheses output
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<?php

echo 'abc' . 'cde' . 'fgh';
echo 'abc' . ('cde' . 'fgh');

echo 'abc' . 1 + 2 . 'fgh';
echo 'abc' . (1 + 2) . 'fgh';

echo 1 * 2 + 3 / 4 % 5 . 6;
echo 1 * (2 + 3) / (4 % (5 . 6));

$a = $b = $c = $d = $f && true;
($a = $b = $c = $d = $f) && true;
$a = $b = $c = $d = $f and true;
$a = $b = $c = $d = ($f and true);

$a ? $b : $c ? $d : $e ? $f : $g;
$a ? $b : ($c ? $d : ($e ? $f : $g));
$a ? $b ? $c : $d : $f;

(1 > 0) > (1 < 0);

$a ** $b ** $c;
($a ** $b) ** $c;

// this will currently unnecessarily print !($a = $b). This is correct as far as operator precedence is concerned, but
// the parentheses are not really necessary, because = takes only variables as the left hand side operator.
!$a = $b;
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echo 'abc' . 'cde' . 'fgh';
echo 'abc' . ('cde' . 'fgh');
echo 'abc' . 1 + 2 . 'fgh';
echo 'abc' . (1 + 2) . 'fgh';
echo 1 * 2 + 3 / 4 % 5 . 6;
echo 1 * (2 + 3) / (4 % (5 . 6));
$a = $b = $c = $d = $f && true;
($a = $b = $c = $d = $f) && true;
$a = $b = $c = $d = $f and true;
$a = $b = $c = $d = ($f and true);
$a ? $b : $c ? $d : $e ? $f : $g;
$a ? $b : ($c ? $d : ($e ? $f : $g));
$a ? $b ? $c : $d : $f;
(1 > 0) > (1 < 0);
$a ** $b ** $c;
($a ** $b) ** $c;
// this will currently unnecessarily print !($a = $b). This is correct as far as operator precedence is concerned, but
// the parentheses are not really necessary, because = takes only variables as the left hand side operator.
!($a = $b);