CODEWITHSUNDEEP
phparrayslogic
FeRtoll
FeRtoll

Reputation: 1267

PHP min and max with array, is it reliable?

This works but, is it reliable? Will it always work since the MAINarray is containing ANOTHERarray which contains 2 values and min should work in MAINarray and find lowest value in its subarays.

$a[0]=array(0=>522,1=>'Truck');
$a[1]=array(0=>230,1=>'Bear');
$a[2]=array(0=>13,1=>'Feather');
$a[3]=array(0=>40,1=>'Rabit');
$z=min($a);$y=max($a);
echo "The easiest is ".$z[1]." with only ".$z[0]." pounds!<br>";
echo "The heaviest is ".$y[1]." with ".$y[0]." pounds!";

What you say?

Upvotes: 3

Views: 1210

Answers (4)

Matthew
Matthew

Reputation: 48304

My understanding of how min works with your type of input is:

  1. Only consider the arrays with the fewest number of items.
  2. Compare the first elements
  3. If there is a tie, compare the next element of each array. Repeat step.

e.g.:

array(
  array(1, "A"),
  array(2),        // min
)


array(
  array(1, "A"),  // min
  array(2, "A"),        
)

array(
  array(1, "Z"),  
  array(1, "A"),  // min
)

I don't have a source for that information, but it's how I remember it working.

Upvotes: 2

user229044
user229044

Reputation: 239462

Yes, it is reliable. It's safe to assume that min(array(1, 2, ..., n)) is equivalent to min(1, 2, ..., n), and the documentation specifically covers how min compares multiple arrays:

// With multiple arrays, min compares from left to right
// so in our example: 2 == 2, but 4 < 5
$val = min(array(2, 4, 8), array(2, 5, 1)); // array(2, 4, 8)

Upvotes: 3

Mike
Mike

Reputation: 923

The only evidence I could find to say it was intended to be able to use an array of arrays to compare is this bug report to improve the php docs. http://bugs.php.net/bug.php?id=50607

Although, it's quite unlikely for them to remove this functionality because of the way it has to compare arrays already by going into them recursively. The arguments list itself when using the function normally would be an array because there is no finite number of arguments.

Upvotes: 0

Gumbo
Gumbo

Reputation: 655609

I’m not sure if this always works. In case of doubt just implement the function yourself:

function extremes($array, $key=0) {
    if (count($array) === 0) return null;
    $min = $max = null;
    foreach ($array as &$val) {
        if (!isset($val[$key])) continue;
        if ($min > $val[$key]) $min = $val[$key];
        else if ($max < $val[$key]) $max = $val[$key];
    }
    return array($min, $max);
}

$a = array(array(522, 'Truck'), array(230, 'Bear'), array(13, 'Feather'), array(40, 'Rabit'));
list($z, $y) = extremes($a);

Upvotes: 1

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