Emitted when --find-dead-code is turned on and Psalm cannot find any
references to the foreach value
<?php
/** @param array<string, int> $a */
function foo(array $a) : void {
foreach ($a as $key => $value) { // $value is unused
echo $key;
}
}Can be suppressed by prefixing the variable name with an underscore or naming
it $_:
<?php
foreach ([1, 2, 3] as $key => $_val) {}
foreach ([1, 2, 3] as $key => $_) {}