PHP - Check if more than one condition is true in a given number of conditions

Question

Is there an elegant way to check if multiple, but not all, conditions are true out of any given number of conditions?

For example, I have three variables: $a, $b, and $c. I want to check that any two of these are true. So the following would pass:

$a = true;
$b = false;
$c = true;

But this wouldn't:

$a = false;
$b = false;
$c = true;

Also, I may want to check if 4 out of 7 conditions were true, for example.

I realise I can check each combination, but this would get more difficult as the number of conditions increased. Looping through the conditions and keeping a tally is the best option I can think of, but I thought there may be a different way to do this.

Thanks!

Edit: Thanks for all the great answers, they're much appreciated. Just to throw a spanner in to the works, what if the variables weren't explicit booleans? E.g.

($a == 2)
($b != "cheese")
($c !== false)
($d instanceof SomeClass)

Answer 1

A "true" boolean in PHP casts to a 1 as an integer, and "false" casts to 0. Hence:

echo $a + $b +$c;

...will output 2 if two out of the three boolean variables $a, $b or $c are true. (Adding the values will implicitly convert them to integers.)

This will also work with functions like array_sum(), so for example:

echo array_sum([true == false, 'cheese' == 'cheese', 5 == 5, 'moon' == 'green cheese']);

...will output 2.

Answer 2

You could put your variables in an array, and use array_filter() and count() to check the number of true values:

$a = true;
$b = false;
$c = true;

if (count(array_filter(array($a, $b, $c))) == 2) {
    echo "Success";
};

Answer 3

I'd go for a method like the following:

if (evaluate(a, b, c))
{
    do stuff;
}

boolean evaluate(boolean a, boolean b, boolean c) 
{
    return a ? (b || c) : (b && c);
}

What it says is:

• If a is True, then one of b or c must be true too to comply with 2/3 True criterion.
• Else, both b and c must be true!

If you want to expand and customise the conditions and the number of variables I'd go for for a solution like the following:

$a = true;
$b = true;
$c = true;
$d = false;
$e = false;
$f = true;

$condition = 4/7;

$bools = array($a, $b, $c, $d, $e, $f);

$eval = count(array_filter($bools)) / sizeof($bools);

print_r($eval / $condition >= 1 ? true : false);

Simply we evaluate the true's and we make sure that the % of True is equals or is better than what we want to achieve. Likewise you could manipulate the final evaluation expression to achieve what you want.

Answer 4

This should also work, and would allow you fairly easily to adjust to the numbers.

$a = array('soap','soap');
$b = array('cake','sponge');
$c = array(true,true);
$d = array(5,5);
$e = false;
$f = array(true,true);
$g = array(false,true);
$pass = 4;
$ar = array($a,$b,$c,$d,$e,$f,$g);

var_dump(trueornot($ar,$pass));

function trueornot($number,$pass = 2){
    $store = array();
    foreach($number as $test){
        if(is_array($test)){
            if($test[0] === $test[1]){
                $store[] = 1;
            }
        }else{
            if(!empty($test)){
                $store[] = 1;   
            }
        }    
        if(count($store) >= $pass){
            return TRUE;    
        }
    }
    return false;
}