Math 函数
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min

(PHP 4, PHP 5)

min — 找出最小值

说明

mixed min ( number $arg1 , number $arg2 )
mixed min ( array $numbers [, array $... ] )

min() 返回参数中数值最小的。

如果仅有一个参数且为数组，min() 返回该数组中最小的值。如果给出了两个或更多参数, min() 会返回这些值中最小的一个。

Note:

PHP 会将非数值的 string 当成 0，但如果这个正是最小的数值则仍然会返回一个字符串。如果多个参数都求值为 0 且是最小值，min() 会返回按字母表顺序最小的字符串，如果其中没有字符串的话，则返回数值的 0。

Example #1 使用 min() 的例子

<?php
echo min(2, 3, 1, 6, 7);  // 1
echo min(array(2, 4, 5)); // 2
echo min(0, 'hello');     // 0
echo min('hello', 0);     // hello
echo min('hello', -1);    // -1

// 对多个数组，min 从左向右比较。
// 因此在本例中：2 == 2，但 4 < 5
$val = min(array(2, 4, 8), array(2, 5, 1)); // array(2, 4, 8)

// 如果同时给出数组和非数组作为参数，则不可能返回数组，因为
// 数组被视为最大的
$val = min('string', array(2, 5, 7), 42);   // string
?>

参见 max() 和 count()。

Math 函数
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PHP手册 - N: 找出最小值

用户评论:

hava82 at gmail dot com (26-Sep-2011 08:35)

Here is function can find min by array key

<?php
function min_by_key($arr, $key){
    $min = array();
    foreach ($arr as $val) {
        if (!isset($val[$key]) and is_array($val)) {
            $min2 = min_by_key($val, $key);
            $min[$min2] = 1;
        } elseif (!isset($val[$key]) and !is_array($val)) {
            return false;
        } elseif (isset($val[$key])) {
            $min[$val[$key]] = 1;
        }
    }
    return min( array_keys($min) );
}
?>

php at keith tyler dot com (23-Nov-2010 09:03)

If NAN is the first argument to min(), the second argument will always be returned.

If NAN is the second argument, NAN will always be returned.

The relationship is the same but inverted for max().

<?php
// \n's skipped for brevity
print max(0,NAN);
print max(NAN,0);
print min(0,NAN);
print min(NAN,0);
?>

Returns:
0
NAN
NAN
0

matt at borjawebs dot com (13-Nov-2010 09:18)

A condensed version (and possible application) of returning an array of array keys containing the same minimum value:

<?php
// data
$min_keys = array();
$player_score_totals = array(
'player1' => 300,
'player2' => 301,
'player3' => 302,
'player4' => 301,
...
);

// search for array keys with min() value
foreach($player_score_totals as $playerid => $score)
    if($score == min($player_score_totals)) array_push($min_keys, $playerid);

print_r($min_keys);
?>

Err (05-Oct-2009 12:32)

When using a variable with an array that has a list of numbers, put just the variable in min(). Don't use integer index's. Seems pretty straight forward now, but I wasn't used to just putting down the variable for an array in functions.

<?php
  $list = array(9,5,4,6,2,7);
  echo min($list); // display 2
?>

andrew dot j dot dodson at gmail (18-Dec-2008 05:10)

min/max works with yyyy-mm-dd dates, e.g.

<?php

$a = array(   '2008-10-01',    '2008-12-01'  );

print min($a); //  '2008-10-01'
print max($a); //  '2008-12-01'

?>

Which is a unexpected since at the top of this page it says.
"PHP will evaluate a non-numeric string as 0"

And if we cast it as an int then we get the year

<?php
print (int)"2008-01-12"; // 2008
?>

ksours at internetbrands dot com (02-Dec-2008 12:07)

PHP_INT_MAX is the MAXINT equivalent

mlester at ndsuk dot com (12-Nov-2008 03:59)

I have found a very useful trick to help get round the problem of setting a variable to max int when finding a min i.e.

<?php
$val = 10;
$min = 100000;  // This is unpleasant and I couldn't find a equivalent to the C++ MAXINT
if ($val < $min)
{
  $min = $val;
}
?>

try this ...

<?php
$dataSet = Array(7, 8, 9, -1, -100, 0, 1, 2, 3, 5, 6);
$min = true;
$max = true;
           
foreach ($dataSet as $data )
{
  echo("data = $data");
  $min = min($data, $min);
  $max = max($data, $max);
}
           
echo("min = $min");
echo("max = $max");
?>

$max can be set to anything e.g. "infinity", but the same trick doesn't work with min, however true does work (false doesn't). Not sure why though.

The above code even works with a data set like this...
<?php $dataSet = Array("0.5", 1, 2, "3", "-1", "5"); ?>

but min doesn't like null or negative float e.g. "-1.2" and "" can give some odd results too.

DO (03-Jul-2008 11:23)

I've modified the bugfree min-version to ignore NULL values (else it returns 0).

<?php
function min_mod () {
  $args = func_get_args();
 
  if (!count($args[0])) return false;
  else {
    $min = false;
    foreach ($args[0] AS $value) {
      if (is_numeric($value)) {
        $curval = floatval($value);
        if ($curval < $min || $min === false) $min = $curval;
      }
    }
  }
 
  return $min;  
}
?>

harmor (21-Feb-2008 05:58)

A way to bound a integer between two values is:

function bound($x, $min, $max)
{
     return min(max($x, $min), $max);
}

which is the same as:

$tmp = $x;
if($tmp < $min)
{
    $tmp = $min;
}
if($tmp > $max)
{
     $tmp = $max;
}
$y = $tmp;

So if you wanted to bound an integer between 1 and 12 for example:

Input:
$x = 0;
echo bound(0, 1, 12).'<br />';
$x = 1;
echo bound($x, 1, 12).'<br />';
$x = 6;
echo bound($x, 1, 12).'<br />';
$x = 12;
echo bound($x, 1, 12).'<br />';
$x = 13;
echo bound($x, 1, 12).'<br />';

Output:
1
1
6
12
12

johngreenbury at australianescapes dot com dot au (30-Jan-2008 01:43)

You will get an "Wrong parameter count" error (PHP 4 and possibly 5) if your array looks like the following:

min(115.23,432.11,0.00,45.76)

The 0.00 creates the error. Convert the 0.00 to a high number such as 10000000000.00 or remove it from the array before running the min() function.

piotr_sobolewski at o2 dot nospampleasenono dot pl (07-Nov-2007 04:11)

Be very careful when your array contains both strings and numbers. This code works strange (even though explainable) way:
var_dump(max('25.1.1', '222', '99'));
var_dump(max('2.1.1', '222', '99'));

dave at dtracorp dot com (14-Aug-2006 04:30)

empty strings '' will also return false or 0, so if you have something like

$test = array('', 1, 5, 8, 44, 22);

'' will be returned as the lowest value

if you only want to get the lowest number, you'll have to resort to the old fashioned loop

// default minimum value
$minVal = 100;
foreach ($test as $value) {
if (is_numeric($value) && $value < $minVal) {
$minVal = $value;
}

johnphayes at gmail dot com (02-May-2006 05:26)

Regarding boolean parameters in min() and max():

(a) If any of your parameters is boolean, max and min will cast the rest of them to boolean to do the comparison.
(b) true > false
(c) However, max and min will return the actual parameter value that wins the comparison (not the cast).

Here's some test cases to illustrate:

1.  max(true,100)=true
2.  max(true,0)=true
3.  max(100,true)=100
4.  max(false,100)=100
5.  max(100,false)=100
6.  min(true,100)=true
7.  min(true,0)=0
8.  min(100,true)=100
9.  min(false,100)=false
10. min(100,false)=false
11. min(true,false)=false
12. max(true,false)=true

steffen at morkland dot com (16-Mar-2006 10:16)

> NEVER EVER use this function with boolean variables !!!
> Or you'll get something like this: min(true, 1, -2) == true;

> Just because of:
> min(true, 1, -2) == min(min(true,1), -2) == min(true, -2) == true;

It is possible to use it with booleans, there is is just one thing, which you need to keep in mind, when evaluating using the non strict comparison (==) anyting that is not bool false, 0 or NULL is consideret true eg.:
(5 == true) = true;
(0 == true) = false;
true is also actually anything else then 0, false and null. However when true is converted to a string or interger true == 1, therefore when sorting true = 1. But if true is the maximum number bool true is returned. so to be sure, if you only want to match if true is the max number remember to use the strict comparison operater ===

(31-Jan-2006 05:37)

NEVER EVER use this function with boolean variables !!!
Or you'll get something like this: min(true, 1, -2) == true;

Just because of:
min(true, 1, -2) == min(min(true,1), -2) == min(true, -2) == true;

You are warned !

DASPRiD d [AT] sprid [DOT] de (06-Jul-2005 02:39)

Here is my slightly modified version of the bugfree min-version. Now the max() function is no longer used in the modification and overall it's fasten up. Would be nice to get some feedback.

<?php
function min_mod () {
  $args = func_get_args();
 
  if (!count($args)) return false;
  else {
    $min = false;
    foreach ($args AS $value) {
      $curval = floatval($value);
      if ($curval < $min || $min === false) $min = $curval;
    }
  }
 
  return $min;   
}
?>

alx5000 at walla dot com (13-Jan-2005 01:16)

If you want min to return zero (0) when comparing to a string, try this:

<?php
min(3,4,";");  // ";"
min(0,min(3,4,";")) // 0
?>

nonick AT 8027 DOT org (24-Jan-2004 03:43)

I tested this with max(), but I suppose it applies to min() too: If you are working with numbers, then you can use:
 
    $a = ($b < $c) ? $b : $c;
 
 which is somewhat faster (roughly 16%) than
 
    $a = min($b, $c);
 
 I tested this on several loops using integers and floats, over 1 million iterations.
 
 I'm running PHP 4.3.1 as a module for Apache 1.3.27.

browne at bee why you dot ee dee you (16-Dec-2003 10:30)

min() can be used to cap values at a specific value. For instance, if you're grading papers and someone has some extra credit, but  that shouldn't make it to the final score:

$pts_possible = 50;
$score = 55;

// Percent will equal 1 if $score/$pts_possible is greater than 1
$percent = min($score/$pts_possible,1);

kieran at mgpenguin dot net (19-Jul-2003 04:28)

Further modifications to the minnum function above.. This is for a project where I had to grab an entire column out of a database consisting of values that might be string, might be string representations of numbers (floating point or integer) or might be NULL, and find the minimum NUMERIC value:

function minnum($numarray){
    //dont use min(), it contains a bug!
    $min=0;
    if ( ! is_array($numarray) ) $numarray = func_get_args();
    if(is_array($numarray)==true){
        $min=max($numarray);
        for($z=0;$z<count($numarray);$z++){
            $curval=floatval($numarray[$z]);
            if(($curval != 0) && ($curval < $min)){
                $min=$curval;
            }
        }
    }
    return $min;
}

Gets the floating point value of each entry and uses this to check whether it's actually a number before checking whether it's the minimum or not. Also contains modifications noted above to use it as a drop in replacement for min - ie multiple values passed.

Merome at wanadoo dot fr (05-Jul-2003 05:40)

Caution : it seems that min() can return a string :

min(";",50)=";" (I expected zero)

calin at php9 dot com (30-May-2003 04:19)

if you have an array like this

$arSrc[0]=14;
$arSrc[1]=16;
$arSrc[2]=13;
$arSrc[3]=17;

then in order to get the min element and its position in the array you can do:

$iMinValue = min($arSrc);
$arFlip = array_flip($arSrc);
$iMinPosition = $arFlip[$iMinValue];

echo
 '<br />min_value=',
 $iMinValue,
 '<br />min_position=',
 $iMinPosition
;

this example works for also for an associative array; of course with numeric values

(08-Jul-2002 10:36)

Re: above example - for a proper drop in replacement for the above, insert

if ( ! is_array($numarray) )
   $numarray = func_get_args();

after
   $min=0;

(For PHP3, check
if (intval(PHP_VERSION) >= 4 && ! is_array($numarray))
   $numarray = func_get_args();
)

kevin at pricetrak dot com (08-Apr-2002 07:47)

The 'undefined' behaviour can bit you badly. I would expect min(undefined, -1000) to return -1000. Not so.

nak2 at mail2000 dot ru (14-Mar-2002 07:36)

If one of elements is undefided, min() result is underfinded too