Scripts

ternary_assignment.php:

<?php
class Foo
{
    public function bar(bool $condition): array
    {
        $result = $condition
            ? ['yes']
            : ['no'];

        return $result;
    }
}

echo "true:\n";
xdebug_start_code_coverage(XDEBUG_CC_UNUSED);
(new Foo)->bar(true);
$c = xdebug_get_code_coverage();
xdebug_stop_code_coverage();
ksort($c[__FILE__]);
foreach ($c[__FILE__] as $l => $s) printf("  Line %2d: %s\n", $l, $s === 1 ? 'EXECUTED' : 'NOT_EXECUTED');

echo "false:\n";
xdebug_start_code_coverage(XDEBUG_CC_UNUSED);
(new Foo)->bar(false);
$c = xdebug_get_code_coverage();
xdebug_stop_code_coverage();
ksort($c[__FILE__]);
foreach ($c[__FILE__] as $l => $s) printf("  Line %2d: %s\n", $l, $s === 1 ? 'EXECUTED' : 'NOT_EXECUTED');

ternary_in_array.php:

<?php
class Foo
{
    public function bar(bool $condition): array
    {
        $result = [
            'key' => $condition
                ? ['yes']
                : ['no'],
        ];

        return $result;
    }
}

echo "true:\n";
xdebug_start_code_coverage(XDEBUG_CC_UNUSED);
(new Foo)->bar(true);
$c = xdebug_get_code_coverage();
xdebug_stop_code_coverage();
ksort($c[__FILE__]);
foreach ($c[__FILE__] as $l => $s) printf("  Line %2d: %s\n", $l, $s === 1 ? 'EXECUTED' : 'NOT_EXECUTED');

echo "false:\n";
xdebug_start_code_coverage(XDEBUG_CC_UNUSED);
(new Foo)->bar(false);
$c = xdebug_get_code_coverage();
xdebug_stop_code_coverage();
ksort($c[__FILE__]);
foreach ($c[__FILE__] as $l => $s) printf("  Line %2d: %s\n", $l, $s === 1 ? 'EXECUTED' : 'NOT_EXECUTED');

Output

ternary_assignment.php (simple variable assignment):

true:
  Line  6: EXECUTED          $result = $condition
  Line  7: EXECUTED              ? ['yes']
  Line  8: NOT_EXECUTED          : ['no'];
  Line 10: EXECUTED          return $result;
  Line 11: NOT_EXECUTED      }
false:
  Line  6: EXECUTED          $result = $condition
  Line  7: NOT_EXECUTED          ? ['yes']
  Line  8: EXECUTED              : ['no'];
  Line 10: EXECUTED          return $result;
  Line 11: NOT_EXECUTED      }

Both branch lines (7 and 8) are reported. Their status correctly reflects which branch was taken.

ternary_in_array.php (ternary as value in array literal):

true:
  Line  6: EXECUTED          $result = [
  Line  7: EXECUTED              'key' => $condition
  Line 12: EXECUTED          return $result;
  Line 13: NOT_EXECUTED      }
false:
  Line  6: EXECUTED          $result = [
  Line  7: EXECUTED              'key' => $condition
  Line 12: EXECUTED          return $result;
  Line 13: NOT_EXECUTED      }

Lines 8 (? ['yes']) and 9 (: ['no']) are absent from the coverage data in both calls. There is no way to determine from the reported data whether either branch was taken.

Analysis

The opcodes generated for bar() in both scripts are structurally identical (shown via opcache.opt_debug_level=0x20000):

ternary_assignment.php             ternary_in_array.php
---------------------              --------------------
RECV                               RECV
JMPZ -> false branch               JMPZ -> false branch
QM_ASSIGN array(...)               QM_ASSIGN array(...)
JMP -> after                       JMP -> after
QM_ASSIGN array(...)               QM_ASSIGN array(...)
QM_ASSIGN T2 (assign)              INIT_ARRAY 1 T2 "key"
RETURN                             RETURN

Both have the same QM_ASSIGN opcodes for the true and false branch values. The difference in coverage output suggests that the opcode-to-line mapping for the QM_ASSIGN opcodes differs between the two contexts: in the simple assignment case each QM_ASSIGN is mapped to its source line (7 and 8); in the array literal case both appear to be mapped to the condition line (7), making lines 8 and 9 invisible to line coverage.