How to create dynamic IF statements without using 'eval' in PHP?

Question

I would like to build an IF statement in PHP using some options that are coming from the Database.

Let's say I get an array like this from the DB:

$db = [
    'number1' => [
        '<= 5',
        '&&'
    ],
    'number2' => [
        '> 200',
        '&&'
    ],
    'number3' => [
        '= 1',
        '||'
    ],
    'number3' => [
        '= 2',
        '||'
    ],
];

I'd like to translate it into this:

if ($data['number1'] <= 5 && 
    $data['number2'] > 200 &&
    ($data['number3'] == 1 || 
     $data['number3'] == 2
    )) {
    // do something
}

Of course, I'd start it by doing a foreach and putting the KEYs of the array into the $data[''] array. However, I'm pretty unsure how can I put the logical operators and everything else in place.

Can anyone give me an idea please?

It becomes complex as you can mix and and or logic, what if you would like brackets to say x and (y or z). — Nigel Ren
– Nigel Ren, Commented May 9, 2018 at 16:19
Are you sure about that starting structure? You can't have two of the same key (number3). — Don't Panic
– Don't Panic, Commented May 9, 2018 at 16:35
@NigelRen Yes exactly it gets pretty complicated, that's why I was wondering how people usually solve this issue. — Radical_Activity
– Radical_Activity, Commented May 9, 2018 at 16:44
@Don'tPanic Actually that's by design, but you're right it's not looking ok inside an array. I just wanted to make a point that I need a solution that covers the case when there are 2 of the same conditions with different values. — Radical_Activity
– Radical_Activity, Commented May 9, 2018 at 16:45

Praveen Kumar Purushothaman · Accepted Answer · 2018-05-09 16:16:45Z

5

It is always better to sanitize data that comes from MySQL or any user produced data, instead of using eval(). For your case, I would suggest having your data split into:

Operator
Operand
Next Logic

And then compare it with the existing ones and then use that. To start with, you can do:

if ($operator == ">=")
  if ($operand >= $value)

Or something similar to build it recursively - this is the key. Hope this helps.

answered May 9, 2018 at 16:16

Praveen Kumar Purushothaman

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Eakethet · Accepted Answer · 2018-05-09 16:45:08Z

1

Well, sounds quite strange, but I've tried small code example: https://3v4l.org/h21gv

<?php

$arr = [
    'number1' => [
        'value' => 2,
        'comparator' => '<=',
        'compareTo' => 5,
        'next' => '&&'
    ],
    'number2' => [
        'value' => 230,
        'comparator' => '>',
        'compareTo' => 200,
        'next' => '&&'
    ],
    'number3' => [
        'value' => 1,
        'comparator' => '==',
        'compareTo' => 1,
        'next' => '||'
    ],
    'number3' => [
        'value' => 2,
        'comparator' => '==',
        'compareTo' => 2,
        'next' => '||'
    ],
];



function comparator(array $ar) {
    $i = 0;
    $m = count($ar);
    $last = true;
    foreach ($ar as $compare) {
        $i++;
        switch($compare['comparator']) {
            case '<=':
                $bool = $compare['value'] <= $compare['compareTo'];
                break;
            case '>':
                $bool = $compare['value'] > $compare['compareTo'];
                break;
            case '==':
                $bool = $compare['value'] == $compare['compareTo'];
                break;
        }
        if ($i < $m) {
            switch($compare['next']) {
            case '||':
                $last = $last || $bool;
                break;
            case '&&':
                $last = $last && $bool;
                break;
            }
        }
    }
    return $last;
}

var_dump(comparator($arr));

edited May 9, 2018 at 16:45

answered May 9, 2018 at 16:24

Eakethet

6721 gold badge5 silver badges18 bronze badges

2 Comments

Nigel Ren Over a year ago

The 'comparator' in your last part of your test array has only 1 '='

Eakethet Over a year ago

@NigelRen thanks, had a typo also in switch, didnt notice this one

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