Windows which

winwhich.bat

@echo off
php %USERPROFILE%\bin\winwhich.php %*

winwhich.php

<?php

$PATH = explode(';', getenv('PATH'));
$PATHEXT = explode(';', getenv('PATHEXT'));

$showCandidates = false;
$file = '';

array_shift($argv);

foreach ($argv as $arg) {
    if ($arg == '--show-candidates') {
        $showCandidates = true;
    } else {
        $file = $arg;
    }
}

if (empty($file)) {
    echo 'No file given!', PHP_EOL;
    return 1;
}

array_unshift($PATHEXT, '');

$candidates = array();

foreach ($PATHEXT as $ext) {
    $fn = $file . $ext;

    foreach ($PATH as $p) {
        $candidates[] = $p . '\\' . $fn;
    }
}

foreach ($candidates as $c) {
    $exists = file_exists($c);

    if ($showCandidates) {
        echo ($exists ? 'yes' : 'no '), ' ', $c, PHP_EOL;
    } elseif (!$showCandidates && $exists) {
        echo $c, PHP_EOL;
    }
}

return 0;