Check if multiple values are all false or all true

问题

How can I check if 20 variables are all true, or if 20 variables are all false?

if possible without using a really long if ...

the variables are actually array elements:

array('a'=> true, 'b'=> true ...)

to make it more clear:

if the array has both true and false values return nothing
if the array has only true values return true
if the array has only false values return false :)

回答1:

if(count(array_unique($your_array)) === 1)  
  return current($your_array);

else return;

回答2:

You could use in_array

Ex. for all true:

if(in_array(false, $array, true) === false){
    return true;
}
else if(in_array(true, $array, true) === false){
    return false;
}
else{
     return 'nothing';
}

回答3:

One can use array_product as demonstrated at php.net in a comment:

$check[] = boolval(TRUE);
$check[] = boolval(1);
$check[] = boolval(FALSE);
$check[] = boolval(0);

$result = (bool) array_product($check);
// $result is set to FALSE because only two of the four values evaluated to TRUE

回答4:

This question is ancient, but no matter. I wanted to benchmark the different approaches. The in_array() method performs best since it probably doesn't need to iterate through the whole array. (Odds are low you'd have but one unique boolean at the end, but even then it performs well.)

One approach not mentioned here is array_sum($array), which returns 0 if all values are false, and 1+ if there's a true value somewhere. Like the array_filter approach, it won't tell you if both are present, but is useful for finding out if anything is true. I also added in a basic foreach check for mixed or all true/false, and an in_array that just checks if anything is true (as *_bin below).

So here are the benchmarks. Each case is iterated 100000 times with an array of 10, 100 or 1000 random booleans; and again with 9, 99 and 999 identical booleans, with the last one unique (to have full iteration time for in_array). First three checks tested produce the requested true/false/both result, and the remaining four simply check if a true value is present.

RANDOM BOOLEANS

in_array: 10 bools = 0.16 sec
foreach: 10 bools = 0.122 sec
array_unique: 10 bools = 0.274 sec
foreach_bin: 10 bools = 0.095 sec
in_array_bin: 10 bools = 0.073 sec
array_sum: 10 bools = 0.074 sec
array_filter: 10 bools = 0.118 sec

in_array: 100 bools = 0.153 sec
foreach: 100 bools = 0.122 sec
array_unique: 100 bools = 2.3451 sec
foreach_bin: 100 bools = 0.094 sec
in_array_bin: 100 bools = 0.074 sec
array_sum: 100 bools = 0.126 sec
array_filter: 100 bools = 0.228 sec

in_array: 1000 bools = 0.154 sec
foreach: 1000 bools = 0.149 sec
array_unique: 1000 bools = 32.6659 sec (!!)
foreach_bin: 1000 bools = 0.075 sec
in_array_bin: 1000 bools = 0.074 sec
array_sum: 1000 bools = 0.8771 sec
array_filter: 1000 bools = 1.4021 sec

LAST BOOLEAN DIFFERS

in_array: 10 bools = 0.152 sec
foreach: 10 bools = 0.342 sec
array_unique: 10 bools = 0.269 sec
foreach_bin: 10 bools = 0.074 sec
in_array_bin: 10 bools = 0.076 sec
array_sum: 10 bools = 0.074 sec
array_filter: 10 bools = 0.121 sec

in_array: 100 bools = 0.159 sec
foreach: 100 bools = 2.8072 sec
array_unique: 100 bools = 2.7702 sec
foreach_bin: 100 bools = 0.074 sec
in_array_bin: 100 bools = 0.09 sec
array_sum: 100 bools = 0.118 sec
array_filter: 100 bools = 0.248 sec

in_array: 1000 bools = 0.312 sec
foreach: 1000 bools = 27.5256 sec
array_unique: 1000 bools = 42.1594 sec
foreach_bin: 1000 bools = 0.074 sec
in_array_bin: 1000 bools = 0.24 sec
array_sum: 1000 bools = 0.555 sec
array_filter: 1000 bools = 1.3601 sec

Then, in summary. The array_unique way clearly holds the tail, don't use for large arrays or large volumes of arrays! The foreach way has a slight edge over in_array, but alas the code isn't quite as elegant. The array_sum way is on par with the "if true" checks for smaller (<100) arrays. (I dig the simplicity in array_sum($array) > 0.) The array_filter way lags a bit behind in_array and foreach. When only the last value differs, foreach and array_unique both drag it bad.

Finally, the foreach function for good humors. Very readable. The truth is out there!

function foreach_truth_test($array)
{   
    $trues = $falses = false;

    foreach($array as $val) {
        if ($val === true) {
            $trues = true;
        } elseif ($val === false) {
            $falses = true;
        }
        if ($trues === true && $falses === true) {
            return 'both'; // Enough information.
        }
    }

    // Regular Universe
    if ($trues === true && $falses === false) {
        return 'true';
    } // Evil Mirror Universe
    elseif ($trues === false && $falses === true) {
        return 'false';
    } // Intergalactic Void
    else {
        return 'void'; // =^_^=
    }
}

P.S. Could use 'null' above, but it reads more fun this way around. Benchmarked on Windows so the microtime readings are chunky.

回答5:

If you store only booleans, use this:

$a = array('a'=> true, 'b'=> true, 'c'=>true);
$af = array_filter($a);
if ($af == $a) {
    echo "all true";
}
if (empty($af)) {
    echo "all false";
}

Note: if you have other values in the array they will be converted to boolean according to the horrific conversion rules of PHP.

回答6:

A simple loop will do. Mind that if the array is empty, both conditions are met (all false and all true). You won't see this in the result, because of the else, but you can find out yourself how you want to handle this.

// Input
$x = array ('a'=>false, 'b'=>false, 'c'=>false);

// Initialization
$anytrue = false;
$alltrue = true;

// Processing
foreach($x as $k=>$v)
{
    $anytrue |= $v;
    $alltrue &= $v;
}

// Display result
if ($alltrue)
  echo 'All elements are true';
elseif (!$anytrue)
  echo 'All elements are false';
else
  echo 'Mixed values';

回答7:

If they're all array elements, with true/false values, then use array_flip():

~~$new = array_flip($array); if (!isset($array[false]) && isset($array[true])) { ... there's no false values, and at least one true value }~~

This could get expensive for a large array, so you may want to try array_unique() instead. You'd get an array with at most two values (one true, one false).

Ok, so that wouldn't work. Simple shotgun approach:

if (in_array($yourarray, false, TRUE)) {
   ... at least one non-true value
}

回答8:

More over you can have a list o variables (not only an array of values) to check all the values against a certain value.

$var1 = true;
$var2 = true;
$var3 = false;

$isAllVarsTrue = !in_array(false, [$var1, $var2, $var3], true);

var_dump($isAllVarsTrue); //false

回答9:

Use a for loop. If you want to check that all variables are false you can use a for loop: once you find a true element you can break the cycle, otherwise variables are all false. Same method you can use if you want to check that all variables are true.

回答10:

// set default value
$result = false;

foreach ($array as $key => $value) {
    if ($value === true) {
        $result = true;
        break;
    } 
}

// $result is now true if any value was true, otherwise it's false

来源：https://stackoverflow.com/questions/6850452/check-if-multiple-values-are-all-false-or-all-true

标签

php

conditional

boolean

conditional-statements

boolean-logic