[RESOLVED] Get string between

JamesBrauman

Hello,
I am trying to write a function to get the string between two other strings in a string of text.
This is what I have so far:

	function retrieveBetween($subject, $start, $end) {
		$matchPattern = "/.*$start.*$end.*/";
		if (preg_match($matchPattern, $subject, $matches)) {
			return $matches[0];
		} else {
			return "Could not find valid match.";
		}
	}

However it keeps returning "could not find valid match."
I dont think I have a proper handle on regular expressions yet.
Could someone please tell me what is wrong with this code?

Thanks.

HalfaBee

Try $matchPattern = "/$start(.*)$end/"

and return $matches[1]

JamesBrauman

Hm okay I did that and it works well for some strings but other ones (that use special characters) fail... example:

//fails
echo retrieveBetween("my what a [[good day it[] is today!", "[[", "[]");

HalfaBee

You need to escape the [ s

echo retrieveBetween("my what a [[good day it[] is today!", "\[\[", "\[]");

Weedpacket

HalfaBee wrote:
You need to escape the [ s

And you can use [man]preg_quote[/man] to do that.

JamesBrauman

Thread resolved. I used a little snippet I found on the net.

Could come in handy for someone:

	function get_string_between($string, $start, $end){
	        $string = " ".$string;
	        $ini = strpos($string,$start);
	        if ($ini == 0) return "";
	        $ini += strlen($start);   

	        $len = strpos($string,$end,$ini) - $ini;
	        return substr($string,$ini,$len);
	}

Weedpacket

That was obviously written by someone who doesn't know how to use [man]strpos[/man] to see if a substring exists (the code given risks bugs if for some wacky reason you want $start to start with a space).
You can replace the first three lines with

$ini = strpos($string, $start);
if($ini===false) return "";

But I was bored: I thought I'd find a different way to do it. Without strpos or substr.

function get_string_between($string, $start, $end){
	$chunk = explode($start, $string, 2);
	if(count($chunk)==1) return "";
	$chunk = explode($end, $chunk[1], 2);
	if(count($chunk)==1) return "";
	return $chunk[0];
}

Weedpacket

$ini = strpos($string, $start);
if($ini===false) return "";

But I was bored: I thought I'd find a different way to do it. Without strpos or substr.

function get_string_between($string, $start, $end){
	$chunk = explode($start, $string, 2);
	if(count($chunk)==1) return "";
	$chunk = explode($end, $chunk[1], 2);
	if(count($chunk)==1) return "";
	return $chunk[0];
}