PHP中is_file()函数的定义与使用方法

<?php
var_dump(is_file(&#39;a_file.txt&#39;)) . "\n";
var_dump(is_file(&#39;/usr/bin/&#39;)) . "\n";
?>

<?php
function isfile($file){
return preg_match(&#39;/^[^.^:^?^-][^:^?]*.(?i)&#39; . getexts() . &#39;$/&#39;,$file);
//first character cannot be . : ? - subsequent characters can&#39;t be a : ?
//then a . character and must end with one of your extentions
//getexts() can be replaced with your extentions pattern
}
function getexts(){
//list acceptable file extensions here
return &#39;(app|avi|doc|docx|exe|ico|mid|midi|mov|mp3|
mpg|mpeg|pdf|psd|qt|ra|ram|rm|rtf|txt|wav|word|xls)&#39;;
}
echo isfile(&#39;/Users/YourUserName/Sites/index.html&#39;);
?>

<?php
function deletefolder($path)
{
if ($handle=opendir($path))
{
while (false!==($file=readdir($handle)))
{
if ($file<>"." AND $file<>"..")
{
if (is_file($path.&#39;/&#39;.$file))
{
@unlink($path.&#39;/&#39;.$file);
}
if (is_dir($path.&#39;/&#39;.$file))
{
deletefolder($path.&#39;/&#39;.$file);
@rmdir($path.&#39;/&#39;.$file);
}
}
}
}
}
?>