Regular expression to filter filenames in PHP

I have strings that represent file paths. Something like this.

folder1/folderA/file1.flv  
folder2/folderB/file1.mp4  
folder3/folderC/file1.jpg

I am trying to write an expression that basically matches against a list of valid extensions such as .flv, .mp4, .flv

I am sure I am way off 开发者_开发问答here but here's what I have .[(\.flv/)|(\.wmv/)|(\.mp4)] comical, I'm sure... but hopefully shows the gist.

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As an alternative to a regex, you could use pathinfo() which will reliably get you the file extension from a path.

$allowed_extensions = array("flv", "mp4", "mpeg"); # note: all lowercase

$ext = pathinfo("/folder1/folderA/file1.flv", PATHINFO_EXTENSION);

# Search array of allowed extensions
if (in_array(strtolower($ext), $allowed_extensions))
 echo "Okay";
else
 echo "Fail";

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If I interpret it correctly, you probably just want something like:

/[.](flv|mp4|wmv)$/

The $ ensures that it matches at the end of the string/filename. The alternatives are listed in the parens, and the [.] is just a nicer notation for \.

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$str = "folder1/folderA/file1.jpg";
$found =  preg_match("/[.]+(jpg|flv)$/", $str, $returns);
print_r ($returns);