How to detect a delimiter in a string in PHP?

Question

I am curious if you have a string how would you detect the delimiter?

We know php can split a string up with explode() which requires a delimiter parameter.

But what about a method to detect the delimiter before sending it to explode function?

Right now I am just outputting the string to the user and they enter the delimiter. That's fine -- but I am looking for the application to pattern recognize for me.

Should I look to regular expressions for this type of pattern recognition in a string?

EDIT: I have failed to initially specify that there is a likely expected set of delimiters. Any delimiter that is probably used in a CSV. So technically anyone could use any character to delimit a CSV file but it is more probable to use one of the following characters: comma, semicolon, vertical bar and a space.

EDIT 2: Here is the workable solution I came up with for a "determined delimiter".

$get_images = "86236058.jpg 86236134.jpg 86236134.jpg";

    //Detection of delimiter of image filenames.
        $probable_delimiters = array(",", " ", "|", ";");

        $delimiter_count_array = array(); 

        foreach ($probable_delimiters as $probable_delimiter) {

            $probable_delimiter_count = substr_count($get_images, $probable_delimiter);
            $delimiter_count_array[$probable_delimiter] = $probable_delimiter_count;

        }

        $max_value = max($delimiter_count_array);
        $determined_delimiter_array = array_keys($delimiter_count_array, max($delimiter_count_array));

        while( $element = each( $determined_delimiter_array ) ){
        $determined_delimiter_count = $element['key'];
        $determined_delimiter = $element['value'];
        }

        $images = explode("{$determined_delimiter}", $get_images);

Answer 1

Determine which delimiters you consider probable (like ,, ; and |) and for each search how often they occur in the string (substr_count). Then choose the one with most occurrences as the delimiter and explode.

Even though that might not be fail-safe it should work in most cases ;)

Answer 2

Either you have imploded or built the string yourself and know the delimiter or else you do NOT use explode. If you're not sure about the delimiter, there is no way you're gonna find out with probability 1. As some comments suggest you could build a heuristic approach but that would be a scientific venture.