检查数组中的所有值是否相同 [英] Check if all values in array are the same

问题描述

我需要检查数组中的所有值是否相同.

I need to check if all values in an array equal the same thing.

例如:

$allValues = array(
    'true',
    'true',
    'true',
);

如果数组中的每个值都等于 'true' 那么我想回显 'all tr​​ue'.如果数组中的任何值等于 'false' 那么我想回显 'some false'

If every value in the array equals 'true' then I want to echo 'all true'. If any value in the array equals 'false' then I want to echo 'some false'

知道如何做到这一点吗?

Any idea on how I can do this?

推荐答案

所有值都等于测试值:

// note, "count(array_flip($allvalues))" is a tricky but very fast way to count the unique values.
// "end($allvalues)" is a way to get an arbitrary value from an array without needing to know a valid array key. For example, assuming $allvalues[0] exists may not be true.
if (count(array_flip($allvalues)) === 1 && end($allvalues) === 'true') {


}

或者只是测试你不想要的东西的存在:

or just test for the existence of the thing you don't want:

if (in_array('false', $allvalues, true)) {

}

如果您确定数组中只有 2 个可能的值，请首选后一种方法，因为它效率更高.但如果有疑问，慢程序比不正确的程序要好，所以使用第一种方法.

Prefer the latter method if you're sure that there's only 2 possible values that could be in the array, as it's much more efficient. But if in doubt, a slow program is better than an incorrect program, so use the first method.

如果你不能使用第二种方法，你的数组非常大，而且数组的内容很可能有超过1个值(特别是如果第二个值很可能出现在数组的开头附近)，执行以下操作可能会快得多:

If you can't use the second method, your array is very large, and the contents of the array is likely to have more than 1 value (especially if the 2nd value is likely to occur near the beginning of the array), it may be much faster to do the following:

/**
 * Checks if an array contains at most 1 distinct value.
 * Optionally, restrict what the 1 distinct value is permitted to be via
 * a user supplied testValue.
 *
 * @param array $arr - Array to check
 * @param null $testValue - Optional value to restrict which distinct value the array is permitted to contain.
 * @return bool - false if the array contains more than 1 distinct value, or contains a value other than your supplied testValue.
 * @assert isHomogenous([]) === true
 * @assert isHomogenous([], 2) === true
 * @assert isHomogenous([2]) === true
 * @assert isHomogenous([2, 3]) === false
 * @assert isHomogenous([2, 2]) === true
 * @assert isHomogenous([2, 2], 2) === true
 * @assert isHomogenous([2, 2], 3) === false
 * @assert isHomogenous([2, 3], 3) === false
 * @assert isHomogenous([null, null], null) === true
 */
function isHomogenous(array $arr, $testValue = null) {
    // If they did not pass the 2nd func argument, then we will use an arbitrary value in the $arr (that happens to be the first value).
    // By using func_num_args() to test for this, we can properly support testing for an array filled with nulls, if desired.
    // ie isHomogenous([null, null], null) === true
    $testValue = func_num_args() > 1 ? $testValue : reset($arr);
    foreach ($arr as $val) {
        if ($testValue !== $val) {
            return false;
        }
    }
    return true;
}

注意: 一些答案将原始问题解释为 (1) 如何检查所有值是否相同，而其他答案将其解释为 (2) 如何检查所有值是否相同 和 确保该值等于测试值.您选择的解决方案应该注意这个细节.

Note: Some answers interpret the original question as (1) how to check if all values are the same, while others interpreted it as (2) how to check if all values are the same and make sure that value equals the test value. The solution you choose should be mindful of that detail.

我的前 2 个解决方案回答了 #2.我的 isHomogenous() 函数会回答 #1，或者如果你将第二个参数传递给它，就会回答 #2.

My first 2 solutions answered #2. My isHomogenous() function answers #1, or #2 if you pass it the 2nd arg.

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