PHP函数is_writeable非常奇怪的行为。

我写的PHP代码如下：testfile.php

<?php
$writeok = array("uploads/", "cache/", "templates_c/", "mainfile.php");
$title = "test file php";
$content = "<table align='center'><tr><td align='left'>\n";
$error = false;
foreach ($writeok as $wok) {
echo "<br />"."../".$wok."<br />";
echo fileowner("../".$wok)."<br />";
echo filegroup("../".$wok)."<br />";
echo fileowner("../".$wok)."<br />";
echo substr(sprintf('%o', fileperms("../".$wok)), -4)."<br />";
echo filetype("../".$wok)."<br />";

if (!is_dir("../".$wok)) {


if ( file_exists("../".$wok) ) {
@chgrp("../".$wok, fileowner("../".$wok));
@chmod("../".$wok, 0666);
if (is_writeable("../".$wok)==false) {
$content .= "file ".$wok." is not writeable"."<br />";
$error = true;

}else{
$content .= "file ".$wok." is writeable"."<br />";
}
if (!is_readable("../".$wok)) {
$content .= "file ".$wok." is not readable"."<br />";
$error = true;

}else{
$content .= "file ".$wok." is readable"."<br />";
}

}
} else {
@chgrp("../".$wok, fileowner("../".$wok));
@chmod("../".$wok, 0777);
if (!is_writeable("../".$wok)) {
$content .= "dir ".$wok." is not writeable"."<br />";
$error = true;

}else{
$content .= "dir ".$wok."is writeable"."<br />";
}
if (!is_readable("../".$wok)) {
$content .= "dir ".$wok." is not readable"."<br />";
$error = true;

}else{
$content .= "dir ".$wok." is readable"."<br />";
}
}
}
$content .= "</td></tr></table>\n";

if(! $error) {
$content .= "<p>"."not error"."</p>";


}else{
$content .= "<p>"." error "."</p>";

}

echo $content;

?>



可是执行结果非常奇怪：

../uploads/
0
0
0
0777
dir

../cache/
0
0
0
0777
dir

../templates_c/
0
0
0
0777
dir

../mainfile.php
0
0
0
0666
file
dir uploads/ is not writeable
dir uploads/ is readable
dir cache/ is not writeable
dir cache/ is readable
dir templates_c/ is not writeable
dir templates_c/ is readable
file mainfile.php is not writeable
file mainfile.php is readable



error

到底是什么原因？