How to detect a delimiter in a string in PHP? - 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

I would say this works 99.99% of the cases :)
The basic idea is, that number of valid delimiters should be the same line by line.
This script calculates delimiter count discrepancies between all lines.
Less discrepancy means more likely valid delimiter.
Putting it all together this function read rows and return it back as an array:
function readCSV($fileName)
{
//detect these delimeters
$delA = array(";", ",", "|", "\t");
$linesA = array();
$resultA = array();
$maxLines = 20; //maximum lines to parse for detection, this can be higher for more precision
$lines = count(file($fileName));
if ($lines < $maxLines) {//if lines are less than the given maximum
$maxLines = $lines;
}
//load lines
foreach ($delA as $key => $del) {
$rowNum = 0;
if (($handle = fopen($fileName, "r")) !== false) {
$linesA[$key] = array();
while ((($data = fgetcsv($handle, 1000, $del)) !== false) && ($rowNum < $maxLines)) {
$linesA[$key][] = count($data);
$rowNum++;
}
fclose($handle);
}
}
//count rows delimiter number discrepancy from each other
foreach ($delA as $key => $del) {
echo 'try for key=' . $key . ' delimeter=' . $del;
$discr = 0;
foreach ($linesA[$key] as $actNum) {
if ($actNum == 1) {
$resultA[$key] = 65535; //there is only one column with this delimeter in this line, so this is not our delimiter, set this discrepancy to high
break;
}
foreach ($linesA[$key] as $actNum2) {
$discr += abs($actNum - $actNum2);
}
//if its the real delimeter this result should the nearest to 0
//because in the ideal (errorless) case all lines have same column number
$resultA[$key] = $discr;
}
}
var_dump($resultA);
//select the discrepancy nearest to 0, this would be our delimiter
$delRes = 65535;
foreach ($resultA as $key => $res) {
if ($res < $delRes) {
$delRes = $res;
$delKey = $key;
}
}
$delimeter = $delA[$delKey];
echo '$delimeter=' . $delimeter;
//get rows
$row = 0;
$rowsA = array();
if (($handle = fopen($fileName, "r")) !== false) {
while (($data = fgetcsv($handle, 1000, $delimeter)) !== false) {
$rowsA[$row] = Array();
$num = count($data);
for ($c = 0; $c < $num; $c++) {
$rowsA[$row][] = trim($data[$c]);
}
$row++;
}
fclose($handle);
}
return $rowsA;
}

Answer 3

I have the same problem, I am dealing with a lot of CSV's from various databases, which various people extract to CSV in various ways, sometimes different each time for the same dataset ... Have simply implemented a function like this in my convert base class
protected function detectDelimiter() {
$handle = #fopen($this->CSVFile, "r");
if ($handle) {
$line=fgets($handle, 4096);
fclose($handle);
$test=explode(',', $line);
if (count($test)>1) return ',';
$test=explode(';', $line);
if (count($test)>1) return ';';
//.. and so on
}
//return default delimiter
return $this->delimiter;
}

Answer 4

I made something like this:
$line = fgetcsv($handle, 1000, "|");
if (isset($line[1]))
{
echo "delimiter is: |";
$delimiter="|";
}
else
{
$line1 = fgetcsv($handle, 1000, ";");
if (isset($line1[1]))
{
echo "delimiter is: ;";
$delimiter=";";
}
else
{
echo "delimiter is: ,";
$delimiter=",";
}
}
This simply checks whether there is a second column after a line is read.

Answer 5

I am having the same issue. My system will recieve CSV files from the client but it could use ";", "," or " " as delimiter and I wnat to improve the system so the client dont have to know which is (They never do).
I search and found this library:
https://github.com/parsecsv/parsecsv-for-php
Very good and easy to use.