root/keywords.php

<?php
/**
* Gets a list of files from a base directory.
* Recursively descends into subdirectories.
*/
function getFileList($base, $dir = null)
{
    if ($dir === null) {
        $dir = $base;
    }
    
    $list = array();
    foreach (scandir($dir) as $name) {
    
        if (substr($name, 0, 1) == '.') {
            // skip these files
            continue;
        }
        
        $result = "$dir/$name";
        
        if (is_dir($result)) {
            // recurse into the subdirectory
            $sub = getFileList($base, $result);
            $list = array_merge($list, $sub);
        } else {
            // strip off the starting base point and slash
            $pos = strlen($base) + 1;
            $list[] = substr($result, $pos);
        }
    }
    
    asort($list);
    return $list;
}

$cmd = 'svn propset svn:keywords "Id"';

passthru("$cmd ./trunk/Solar.php");

$base = './trunk/Solar/';
foreach (getFileList($base) as $name) {
    $file = $base . $name;
    passthru("$cmd $file"); 
}