Detecting File Format in PHP - php

Question

I am building a tool that will accept a CSV or tab-delimited file, which will then be parsed and the data databased.
The uploaded file can be CSV or tab-delimited.
I came up with a workable solution (below) for detecting what format the file might be in and would like to know if there is a better way to solve this and/or how any of you out there have solved the same problem.
Thanks
<?php
$csv_comma='Fruit,Color
Apple,"Red,Green"
Tomato,"Red,Green"
Banana,Yellow
Tangerine,Orange
';
$csv_semi_colon='Fruit;Color
Apple;"Red,Green"
Tomato;"Red,Green"
Banana;Yellow
Tangerine;Orange
';
$tab_delimited='Fruit Color
Apple Red,Green
Tomato Red,Green
Banana Yellow
Tangerine Orange';
$fileArr = array($csv_comma,$csv_semi_colon,$tab_delimited);
foreach($fileArr as $file){
if(preg_match('/^(.+),(.+)/',trim($file))){
echo "CSV with comma separator";
}
if(preg_match('/^(.+);(.+)/',trim($file))){
echo "CSV with semi colon separator";
}
if(preg_match('/^(.+)\t(.+)/',trim($file))){
echo "Tab delimited";
}
}

Answer 1

Well csv has this prety much implemented.
Default for csv is , but with sep= you could specify an other seperator.
You could just implement this as csv. So you have a default of , but if the sep is defined you use that.
You file could look like:
apple, orange, tomato
or
sep=;
apple; orange; tomato
So if the first line starts with sep, it is an "option" line otherwise there are values. For tab you do sep=\t
Now users can define there own seperator and no guessing any more
After some comments of CBroe of easy to use for the user there could be some changes. csv only accepts one charachter as septerator so that system could be use like the above. cvs editor (like excel) will handle that for the user
If the user uses the tab it won't be a csv file but a .txt (for example). So you could change the default according to the file given.
Also I want to add, already pointed out in the comments, if you want to guess you will hit a point where it will occure it is wrong.
I don't know the setup of the files but csv lines need to be the same length (according to my memory). So what you could do is read out the first x lines. and use every seperator.
After that you check which lines lengths are the same, most likely that is your seperator (again guessing)

Answer 2

You can use this kind of pattern to check the csv structure and determine the separator:
if (preg_match('^(?:("[^"]++"|[^,;\t\n]++)(?<sep>[,\t;])(?1)(?:\n|$))++$', $csv_comma, $match))
print_r($match['sep']);