减少所有可能性的条件数

Here is my code to check the number of possible conditions for two elements, Is there a way to reduce the number of checking conditions (not any specific rule for checking).

Why i am asking is, I fear that if I add an additional element it will maximise the checking conditions in a vast manner.

How can I do this?

Here is my code:

<?php
$A = 'alpha';
$B = 'beta';

$result = '';

if($A != '' && $B !='')  
{
    $result .= 'Both has Value';
    // both contains value
}
elseif($A != '' && $B =='')
{
    $result .= 'Only A';
     // only a contains value
}
elseif($A == '' && $B !='') 
{
    $result .= 'Only A';
    // only b contains value
}
else 
{
    $result .= 'Both are Empty';
    // both contains no value
}

echo $A.' - '.$B.'<br>';
echo $result;
?>

Try this...

<?php

$a="123";
$b="";
$c="33";
$result="";
if($a !="")
{
if($result=="")
{
$result .="a"; //Get value $a only
} else {

$result .=" and a"; //Get  value $a with $b or $c    
}
}
if($b !="" )
{
if($result=="")
{
$result .="b"; //Get value $b only
} else {

$result .=" and b"; //Get  value $b with $a or $c    
}
}
if($c !="")
{
if($result=="")
{
$result .="c";  //Get value $c only
} else {

$result .=" and c"; //Get  value $c with $b or $a   
}
}
echo $result;
?>

how about this? i just removed the excess checking.

if($A && $B)  
{
    $result .= 'Both has Value';
    // both contains no value
}
elseif($A)
{
    $result .= 'Only A';
     // only a contains value
}
elseif($B) 
{
    $result .= 'Only B';
    // only b contains value
}
else 
{
    $result .= 'Both are Empty';
    // both contains value
}

echo $A.' - '.$B.'<br>';
echo $result;

Use boolean flags in a result. In this case bit 0 (0 or 1) indicates A is empty or not and bit 2 (0 or 2) indicates B is empty.

$flags = 0;
if  ($A != '')
    $flags |= 1;   //  Binary 0001 = 1
if  ($B != '')
    $flags |= 2;   //  Binary 0010 = 2
$rMsg = array ("Both empty", //  0 : 0000
               "A only",     //  1 : 0001
               "B only",     //  2 : 0010
               "Both full"); //  3 : 0011

$result .= $rMsg [$flags];

I figure you are looking for a useful principal rather than the exact details. Is this what you had in mind?

More generally, given an array of items (up to 32 or 64 depending on MAX_INT):

$flags = 0;
for ($i = 0; $i < count ($items); $i++)
    if  ($items [$i] != '')
        $flags |= 1<<$i;
//  Flags start at bit 0
//  To check if items 3, 7 and 10 are all filled:
$check = (1<<3)|(1<<7)|(1<<10);
if  ($flags & $check == $check)
    echo "all set!";
//  To check if items 0, 5 and 8 are all empty:
    $check = (1<<0)|(1<<5)|(1<<8);
if  ($flags & ~$check == 0)
    echo "all clear!";

Check this program which i created only for this question.Here take your variables in an array. You can take any no. of elements.

$array = array('alpha','beta','theta','gamma');
$result = array();
$final = '';
foreach($array as $key=>$value)
{
    if($value != '')
    {
        array_push($result,$value);
        if(sizeof($result) == 1)
            $final .= $value;
            else
        $final .= ','.$value;
    }
}
if(sizeof($result) == 0)
    echo "All are Empty";

elseif(sizeof($result) == sizeof($array))
    echo "All are Value";

else{
    echo "Only ".$final;
}

In a more abstract way, this useful little function:

function partition($ary, $predicate) {
    $result = [[], []];
    foreach($ary as $item)
        $result[$predicate($item) ? 1 : 0] []= $item;
    return $result;
}

splits an array into two parts based on some criteria, given as a boolean function. Applied to your specific problem:

$data = array('a', 'b', 'c', '');

list($bad, $good) = partition($data, 'boolval');

if(!$good)
    echo 'all are falsy';
elseif(!$bad)
    echo 'all are truthy';
else {
    echo 'bad  items: '; print_r($bad);
    echo 'good items: '; print_r($good);
}