How to check if comma separated strings have duplicate values in php - php

Question

I have a variable that contains comma separated strings and I would like to create a check if this variable has duplicate strings inside without converting it into an array. If it would make it any easier, each comma separated strings have 3 characters.
example.
$str = 'PTR, PTR, SDP, LTP';
logic: if any of the strings has a duplicate value then display an error.

Answer 1

This should work for you:
Just use strtok() to loop through each token of your string, with , as delimiter. Then use preg_match_all() to check if the token is more than once in the string.
<?php
$str = "PTR, PTR, SDP, LTP";
$tok = strtok($str, ", ");
$subStrStart = 0;
while ($tok !== false) {
preg_match_all("/\b" . preg_quote($tok, "/") . "\b/", substr($str, $subStrStart), $m);
if(count($m[0]) >= 2)
echo $tok . " found more than 1 times, exaclty: " . count($m[0]) . "<br>";
$subStrStart += strlen($tok);
$tok = strtok(", ");
}
?>
output:
PTR found more than 1 times, exaclty: 2

Answer 2

You are going to run into some issues with just using explode. In your example, if you use explode, you'll get:
'PTR', ' PTR', ' SDP', ' LTP'
You have to map trim in there.
<?php
// explode on , and remove spaces
$myArray = array_map('trim', explode(',', $str));
// get a count of all the values into a new array
$stringCount = array_count_values($myArray);
// sum of all the $stringCount values should equal size of $stringCount IE: they are all 1
$hasDupes = array_sum($stringCount) != count($stringCount);
?>