Split strings in array to form three-element subarrays - php

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',
),
)

Answer 2

This is my aproach using foreach, explode and array functions:
$strings = [
'SalesOrderNumber=SOH123',
'CustomerID=1',
'BigOrEqual>=44',
'SmallOrEqual<=67',
'NotEqual!=123',
'NotEqual<>2000',
'Smaller<21',
'Bigger>12',
];
function explodeOperators(array $strings) : array
{
$operators = ['>=','<=','!=','<>','<','>','=']; // do not change this order
$result = [];
foreach ($strings as $expression) {
$found = false;
foreach ($operators as $operator) {
$exploded = explode($operator, $expression);
if (count($exploded) > 1 and $found === false) {
$found = true;
array_splice($exploded, 1, 0, $operator);
$result[] = $exploded;
}
}
}
return $result;
}
$result = explodeOperators($strings);
print_r($result);
That will result:
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
)
)