PHP Regular Expression Problem

Question

I have a string which I store book pages. It's something like this:

///0///
Page1 Text
///1///
Page2 Text
///2///
Page3 Text
///3///

I want to extract page texts (Page1 Text, Page2 Text, Page3 Text). Here is the Regular Expression which is am using:

$format = "%///\d*///(.*)///\d*///%";
preg_replace_callback($format, "process_page", $text);

According to this page I can use other character than / in the start and end of the expression. So I used % to simplify my pattern, so I don't have to use escape character like this \/

It seems okay to me, but it return nothing. Can somebody please tell me where is the problem?

Why not to delete every line that begins with ///?

sidyll
– sidyll

2011-03-08 16:28:20 +00:00
Commented Mar 8, 2011 at 16:28 — sidyll
– sidyll, Commented Mar 8, 2011 at 16:28

user142162 · Accepted Answer · 2011-03-08 16:31:13Z

2

I think preg_split might be a better option for you:

$text = '
Page1 Text
///1///
Page2 Text
///2///
Page3 Text
';

$format = "%///\d+///%";
$arr = preg_split($format, $text);

// $arr = Array
// ( 
//     [0] => Page1 Text
//
//     [1] => 
// Page2 Text
// 
//     [2] => 
// Page3 Text
// )

Each page is now in it's own array element.

answered Mar 8, 2011 at 16:31

user142162

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1 Comment

bman Over a year ago

Works like a charm. I'm playing with this more than 10 hour with no result. preg_split is fantastic function which unfortunately I was not familiar with. Thanks!

Czechnology · Accepted Answer · 2011-03-08 16:32:57Z

2

I think you need the s modifier: $format = "%///\d*///(.*)///\d*///%s";

s (PCRE_DOTALL)

If this modifier is set, a dot metacharacter in the pattern matches all characters, including newlines. Without it, newlines are excluded. This modifier is equivalent to Perl's /s modifier. A negative class such as [^a] always matches a newline character, independent of the setting of this modifier.

I'm not sure what you're tryingto do but personally I wouldn't use regex for this. you know the exact string to look for (eg ///4///) and from there the end string (///5/// or end of file). A simle substr with strpos might be a better option.

answered Mar 8, 2011 at 16:32

Czechnology

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2 Comments

bman Over a year ago

Actually a book can contain up until 1000 pages. Regular expression is much easier.

Czechnology Over a year ago

@Mani, what do you mean with "easier"? Is it faster?

Floern · Accepted Answer · 2011-03-08 16:38:39Z

2

I would use something like preg_spilt (see Tim Cooper's answer).

But for your RegEx, try this:

$format = "%///\d+///(.*?)(?=///\d+///)%s";

With Look-around assertion and s-modifier.

answered Mar 8, 2011 at 16:38

Floern

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1 Comment

bman Over a year ago

I am newbie in Regular Expression. I learn about Assertion recently, But I forgot to use it here. Thank for the tip.

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