Check if string is a comma-separated list of digits - php

Question

In my table1 i have varchar field where i store an id-list of other table2 (id - INT UNSIGNED AUTOINCREMENT), separated by comma.
For example: 1,3,5,12,90
Also ids should not be repeated.
I need to check if a string (coming from outside) matches this rule.
For example i need to check $_POST['id_list']
Data consistency is not important for now (for example insert this value without checking if this ids really exist in table2)
Any advice will be helpful.

Answer 1

The easiest way to do such check is to use regular expression (preg_match).
Lets try to find a pattern matching our rule.
Just comma-separated digits:
^[0-9]+(,[0-9]*)*$
^ - means start of string.
$ - means end of string.
[0-9]+ - means that our string MUST starts with a digits.
(,[0-9]+)* - means that our string CAN continue itself with ",$someDigits" manner, from 0 to as many you wish times.
But if our digits are "INT UNSIGNED AUTOINCREMENT" we should modify our pattern this way:
^[1-9][0-9]*(,[1-9][0-9]+)*$
to exclude cases like: 0,01,02,009,000,012
As for unique values, i think more clear will be to use splitting (explode) string by comma to array, pass it through array_unique and compare.
So the result check-function will be:
function isComaSeparatedIds($string, $allowEmpty = false) {
if ($allowEmpty AND $string === '') {
return true;
}
if (!preg_match('#^[1-9][0-9]*(,[1-9][0-9]*)*$#', $string)) {
return false;
}
$idsArray = explode(',', $string);
return count($idsArray) == count(array_unique($idsArray));
}
Also added $allowEmpty argument if u would like to allow empty strings.

Answer 2

For the sake of completeness I would like to mention the following solution:
<?php
$check = explode(',', $string);
if ($diff = array_diff_key($check, array_filter($check, 'ctype_digit'))) {
// at least one is not a digit
foreach ($diff as $failIndex => $failValue) {
// handle
}
}
For less than 1000 digits in the string this is a little faster than preg_match and as little extra you get the positions and the values that are not a digit.

Answer 3

This is a bit of a cheeky solution,but it sure does the work.
<?php
$a="1,3,5,12,90";
$b=explode(",",$a);
$str='';
for($c=0;$c<count($b);$c++)
{
if (preg_match('/^[0-9]+$/', $b[$c]))
{
$str=$str."Y";
}
}
if(count(array_unique($b))==count($b) && (count($b)==strlen($str)))
{
echo $str;
//FURTHER CODE HERE WHEN ALL ELEMENTS UNIQUE AND VALID NUMBERS
}
else
{
//FURTHER CODE HERE WHEN NOT UNIQUE OR NOT A VALID NUMBERS
}
?>