Split strings in array to form three-element subarrays

Question

I am practising with the AdventureWorks database for now and I will be receiving strings like the following: SalesOrderNumber=SOH123 and CustomerID=1. The strings may not always contain =, as they may be >, <, >=, <=, !=, <>.

Ideally, I would like to split each string into 3 fields - the database column to query, the comparison (e.g. =, >, !=, etc) and the value to search for.

I can achieve what I want with lots of code, comparing character by character, but I am hoping someone can suggest a really simple way to do this, as I am sure this must be a fairly common task for websites.

I don't want to just use the strings as they come through, as I need to sanitise them first. I also don't want to send bad queries to the database that may generate SQL errors.

Answer 1

It is indirect and feasibly inefficient to make calls of explode() within nested loops with break condition.

I recommend preg_split() as the right tool for the job. Create a capture group containing a character class of whitelisted symbols. Allow a maximum of 3 elements as its return value. Use the PREG_SPLIT_DELIM_CAPTURE flag to inform the function to preserve the delimiting comparison operators when exploding the string into three parts.

Code: (Demo)

var_export(
    array_map(
        fn($v) => preg_split(
            '/([!<=>]+)/',
            $v,
            3,
            PREG_SPLIT_DELIM_CAPTURE
        ),
        $array
    )
);

Output:

array (
  0 => 
  array (
    0 => 'SalesOrderNumber',
    1 => '=',
    2 => 'SOH123',
  ),
  1 => 
  array (
    0 => 'CustomerID',
    1 => '=',
    2 => '1',
  ),
  2 => 
  array (
    0 => 'BigOrEqual',
    1 => '>=',
    2 => '44',
  ),
  3 => 
  array (
    0 => 'SmallOrEqual',
    1 => '<=',
    2 => '67',
  ),
  4 => 
  array (
    0 => 'NotEqual',
    1 => '!=',
    2 => '123',
  ),
  5 => 
  array (
    0 => 'NotEqual',
    1 => '<>',
    2 => '2000',
  ),
  6 => 
  array (
    0 => 'Smaller',
    1 => '<',
    2 => '21',
  ),
  7 => 
  array (
    0 => 'Bigger',
    1 => '>',
    2 => '12',
  ),
)