PHP string formatting (substr)

Question

I have a function that outputs a path, here are some results:

http://server.com/subdirectory/subdiretory/2021/12/file.txt
http://server.com/subdirectory/subdiretory/something/else/2016/16/file.txt
http://server.com/subdirectory/subdiretory/2001/22/file.txt
C:\totalmess/mess\mess/2012/06/file.txt

I want to cut everything from these excepting filename and two parent directories, so the ones above will look like:

/2021/12/file.txt
/2016/16/file.txt
/2001/22/file.txt
/20012/06/file.txt

So basically I have to find the third "/" from the end and display it with everything afterwards.

I don't know PHP too good, but I guess this is pretty easy to achieve with substr(), stripos() and strlen(), so:

$string ="http://server.com/subdirectory/subdiretory/2001/22/file.txt"
$end = strlen($string);
$slash = // How to get the right slash using stripos()?
$output = substr($string, $slash, $end);
echo $output;

Is this the right way of doing this, or maybe there's another in-built function that searches for -nth symbols within a string?

Shad · Accepted Answer · 2011-08-17 21:43:20Z

3

I say give up on str functions, just explode, array_slice and implode it =)

$end='/'.implode('/',array_slice(explode('/',$string),-3));

edited Aug 17, 2011 at 21:43

answered Aug 17, 2011 at 21:36

Shad

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2 Comments

John Flatness Over a year ago

You'll, of course, need to re-implode if you do this to get a string back. (Also, you don't need to pass the 3 length argument; array_slice will include up to the end of the array by default.)

Shad Over a year ago

@John, thanks for the note about unnecessary param, i had actually caught the implode before your note ;)

notam2774 · Accepted Answer · 2011-08-17 22:08:26Z

-1

Explode and then implode is real easy. But if you wanted to use a string function instead, you can use strrpos.

$string ="http://server.com/subdirectory/subdiretory/2001/22/file.txt"
$slash = strrpos( $string, '/', -3 ); // -3 should be the correct offset.
$subbed = substr( $string, $slash ); //length doesn't need to be specified.

answered Aug 17, 2011 at 22:08

notam2774

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