Regular expression in PHP preg_replace() yields empty results

Question

I'm struggling with the regular expression syntax needed to simply transform this string:

posts/2012-03-16-23-07_an-awesome-post.md

into this string:

an-awesome-post

using the preg_replace() PHP function. Here's what I've got so far:

preg_replace('posts/[0-9-]*_([a-z-]*).md', '$1', 'posts/2012-03-16-23-07_an-awesome-post.md');

No dice. When I assign the result to a variable and echo() out that variable, I get nothing. My regex syntax is a bit rusty, but Googling around a bit makes me think that, at the very least, I'm on the right track.

mathematical.coffee · Accepted Answer · 2012-03-17 12:53:42Z

7

The regex needs to be surrounded by delimiters.

Try '#posts/[0-9-]*_([a-z-]*).md#' as your $pattern (using '#' as the delimiter).

Also, do you want that . to match a literal dot? Then it has to be escaped by a backslash, as in \..

answered Mar 17, 2012 at 12:53

mathematical.coffee

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1 Comment

Sam Over a year ago

You are a god. Thanks! And for those interested in the resulting pattern, it's: '#posts/[0-9-]*_([a-z-]*)\.md#'

guido · Accepted Answer · 2012-03-17 12:53:55Z

1

preg_replace('/posts\/[0-9-]*_([a-z-]*)\.md/', '$1', 'posts/2012-03-16-23-07_an-awesome-post.md');

answered Mar 17, 2012 at 12:53

guido

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Comments

lukassteiner · Accepted Answer · 2012-03-17 12:55:16Z

1

can you expect the string before "an-awesome-post" always to be the same lenght? And the extension always to be .md?

If so, you can just count the number of chars before and after and cut them away.

For Example:

$string = substr($string, 23);
$string = substr($string, 0, -3);

answered Mar 17, 2012 at 12:55

lukassteiner

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xuqin1019 · Accepted Answer · 2012-03-17 13:43:34Z

1

<?php
$str="posts/2012-03-16-23-07_an-awesome-post.md";
$pattern=array('/([^_]*_)/','/\.md/');
$replacement=array('','');
echo preg_replace($pattern, $replacement, $str);

?>

answered Mar 17, 2012 at 13:43

xuqin1019

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Comments

Eitan T · Accepted Answer · 2012-11-16 09:45:00Z

1

preg_replace('#posts/[0-9-]*_([a-z-]*).md#i', '$1', 'posts/2012-03-16-23-07_an-awesome-post.md');

edited Nov 16, 2012 at 9:45

Eitan T

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answered Mar 17, 2012 at 12:55

Tidy Designs

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