PHPWales 2020 - June 3rd to June 4th

max

(PHP 4, PHP 5, PHP 7)

maxLocaliza o maior valor

Descrição

max ( array $values ) : mixed
max ( mixed $value1 , mixed $value2 [, mixed $... ] ) : mixed

Se o primeiro e único parâmetro é um array, max() retorna o maior valor do array. Se no mínimo dois parâmetros são fornecidos, max() retornará o maior desses valores.

Nota:

Valores de diferentes tipos serão comparados utilizando as regras padrões de comparação. Por exemplo uma string não numérica será comparada a um integer como se fosse 0, mas vários valores não numéricos strings serão comparadas alfabeticamente. O valor atual retornado terá o tipo original, sem nenhuma conversão.

Cuidado

Cuidado ao passar argumentos de vários tipos, o que deixa o resultado de max() imprevisível.

Parâmetros

values

Um array contendo os valores.

value1

Qualquer valor comparável.

value2

Qualquer valor comparável.

...

Qualquer valor comparável.

Valor Retornado

max() retorna o parâmetro considerado o "maior" de acordo com as comparações padrões. Se vários valores de tipos diferenes são considerados iguais (por exemplo, 0 e 'abc') então o primeiro valor será retornado.

Se um array vazio for passado, então FALSE será retornado e um alerta E_WARNING será emitido.

Exemplos

Exemplo #1 Exemplos de max()

<?php
echo max(23167);  // 7
echo max(array(245)); // 5

// A string 'hello' quando comparada com um int é tratado como 0
// Como são iguais na comparação, a ordem influencia o resultado
echo max(0'hello');     // 0
echo max('hello'0);     // hello

// Aqui na prática compara-se -1 < 0, então 'hello' é o maior valor
echo max('hello', -1);    // hello

// Arrays de múltiplos valores e tamanhos diferentes, retora o mais longo
$val max(array(222), array(1111)); // array(1, 1, 1, 1)

// Em arrays de mesmo tamanho compara-se da esquerda para direita
// e nesse exemplo: 2 == 2, mas 5 > 4
$val max(array(248), array(251)); // array(2, 5, 1)

// Se um array e um não array são informados, o array será retornado
// pois é considerado maior que qualquer outro valor
$val max('string', array(257), 42);   // array(2, 5, 7)

// Se um argumento é NULL ou booleano, ele será comparado contra
// outros valores utilizando a regra FALSE < TRUE independente dos tipos envolvidos.
// No exemplo abaixo -10 é tratado como TRUE na comparação
$val max(-10FALSE); // -10

// 0 por outro lado é considerado false, de forma que é "menor que" TRUE
$val max(0TRUE); // TRUE
?>

Veja Também

  • min() - Encontra o menor valor
  • count() - Conta o número de elementos de uma variável, ou propriedades de um objeto

add a note add a note

User Contributed Notes 17 notes

up
33
keith at bifugi dot com
3 years ago
The simplest way to get around the fact that max() won't give the key is array_search:

<?php
$student_grades
= array ("john" => 100, "sarah" => 90, "anne" => 100);
$top_student = array_search(max($student_grades),$student_grades); // john
?>

This could also be done with array_flip, though overwriting will mean that it gets the last max value rather than the first:

<?php
$grades_index
= array_flip($student_grades);
$top_student = $grades_index[max($student_grades)]; // anne
?>

To get all the max value keys:

<?php
$top_students
= array_keys($student_grades,max($student_grades)); // john, anne
?>
up
9
ries at vantwisk dot nl
11 years ago
I had several occasions that using max is a lot slower then using a if/then/else construct. Be sure to check this in your routines!

Ries
up
17
costinu
7 years ago
max(null, 0) = null
max(0, null) = 0
up
11
volch5 at gmail dot com
5 years ago
max() (and min()) on DateTime objects compares them like dates (with timezone info) and returns DateTime object.
<?php
$dt1
= new DateTime('2014-05-07 18:53', new DateTimeZone('Europe/Kiev'));
$dt2 = new DateTime('2014-05-07 16:53', new DateTimeZone('UTC'));
echo
max($dt1,$dt2)->format(DateTime::RFC3339) . PHP_EOL; // 2014-05-07T16:53:00+00:00
echo min($dt1,$dt2)->format(DateTime::RFC3339) . PHP_EOL; // 2014-05-07T18:53:00+03:00
?>

It works at least 5.3.3-7+squeeze17
up
10
Alex Rath
9 years ago
Notice that whenever there is a Number in front of the String, it will be used for Comparison.

<?php

  max
('7iuwmssuxue', 1); //returns 7iuwmssuxu
 
max('-7suidha', -4); //returns -4

?>

But just if it is in front of the String

<?php

  max
('sdihatewin7wduiw', 3); //returns 3

?>
up
1
info at osworx dot net
10 months ago
Be aware if a array like this is used (e.g. values from a shopping cart):
<?php
Array
(
    [
0] => 142,80
   
[1] => 39,27
   
[2] => 22,80
   
[3] => 175,80
)?>
The result will be: 39,27 and not - as expected - 175,80

So, to find the max value, use integer only like:
<?php
Array
(
    [
0] => 14280
   
[1] => 3927
   
[2] => 2280
   
[3] => 17580
)?>
and you will get the correct result: 17580
up
3
johnphayes at gmail dot com
13 years ago
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
up
4
ReVo_
5 years ago
Sometimes you could need to get the max from an array which looks like this:

<?php
$arrTest
= array(
    array(
"day" => 1, "b" => 10 ),
    array(
"day" => 2, "b" => 43 ),
    array(
"day" => 3, "b" => 2 ),
    array(
"day" => 4, "b" => -3 ),
    array(
"day" => 5, "b" => 4 ),
    array(
"day" => 6, "b" => -5 )
);
?>
all max functions i see around don't provide a way to get the max value of the values in (example) key "b"

<?php
function maxValueInArray($array, $keyToSearch)
{
   
$currentMax = NULL;
    foreach(
$array as $arr)
    {
        foreach(
$arr as $key => $value)
        {
            if (
$key == $keyToSearch && ($value >= $currentMax))
            {
               
$currentMax = $value;
            }
        }
    }

    return
$currentMax;
}

//                                            array       key
$value = maxValueInArray($arrTest, "b");

?>

output: 43
up
2
php at rijkvanwel dot nl
8 years ago
To get the largest key in an array:

<?php
$array
= array( 0 => 'first', 1=> 'second', /* ... */ 99 => 'nth' );
$max_key = max( array_keys( $array ) ); // 99
?>
up
2
michaelangel0 at mail.com
12 years ago
Matlab users and others may feel lonely without the double argument output from min and max functions.

To have the INDEX of the highest value in an array, as well as the value itself, use the following, or a derivative:

<?php
function doublemax($mylist){
 
$maxvalue=max($mylist);
  while(list(
$key,$value)=each($mylist)){
    if(
$value==$maxvalue)$maxindex=$key;
  }
  return array(
"m"=>$maxvalue,"i"=>$maxindex);
}
?>
up
1
blackmac01 at gmail dot com
2 months ago
In response to: keith at bifugi dot com

If you want to find the specific key(s) that match the maximum value in an array where the values may be duplicated, you can loop through and perform a simple check:
<?php

# Example Array
$a = array(
    
'key1' => 100,
    
'key2' => 90,
    
'key3' => 100,
    
'key4' => 90,
);

# First get the maximum value
$max = max($a);

# Create a new array containing all keys which have the max value
foreach($a as $key => $val) {    
     if(
$val === $max) $b[] = $key;
}

# If you want a string list, just do this
$b = implode(' ', $b);
?>

This produces consistent results and will scale well in terms of performance, whereas functions like array_search and array_flip can lead to degraded performance when dealing with large amounts of data.
up
1
sun at drupal dot org
8 years ago
Note that max() throws a warning if the array is empty:

<?php
$a
= array();
max($a);
// Warning: max(): Array must contain at least one element
?>

So make sure your data isn't empty.
up
1
harmor
11 years ago
A way to bound a integer between two values is:

<?php
function bound($x, $min, $max)
{
     return
min(max($x, $min), $max);
}
?>

which is the same as:

<?php
$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:
<?php
$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
up
-1
marcini
10 years ago
Note that max() can compare dates, so if you write something like this:

<?php
$dates
= array('2009-02-15', '2009-03-15');
echo
max($dates);
?>

you will get: 2009-03-15.
up
-2
toon dot baeyens at gmail dot com
7 years ago
A little function for multi-dimensional arrays:
<?php
function amax($array){
    if(
is_array($array)){
        foreach(
$array as $key => $value){
           
$array[$key] = amax($value);
        }
        return
max($array);
    }else{
        return
$array;
    }
}
?>
up
-2
levim at php dot net
7 years ago
<?php
/**
* @param array $array
*
* @return int|null Returns the largest value of the array. Returns NULL if no
*     integers are found.
*/
function array_max_recursive(array $array) {
   
$max = NULL;
   
$stack = array($array);

    do {
       
$current = array_pop($stack );
        foreach (
$current as $value) {
            if (
is_array($value)) {
               
$stack[] = $value;
            } elseif (
filter_var($value, FILTER_VALIDATE_INT) !== FALSE) {
               
// max(NULL, 0) returns NULL, so cast it
               
$max = (int) max($max, $value);
            }
        }

    } while (!empty(
$stack));

    return
$max;
}
?>

- This function is not actually recursive, but fulfills the requirement that it works on sub-arrays.  I do this because PHP is not very good at recursion.  I also did it because I enjoy doing things this way. 
- It returns something of type int, never a string representation of an int. The exception is when you provide an array that does not contain any integers.  It will then return NULL.
- It ignores non-array, non-int values.
up
-3
Michael Blinn
9 months ago
Be careful using max() with objects, as it returns a reference not a new object.

<?php

$min_date
= date_create('2019-03-05');
$max_date = date_create('2019-03-06');

$date_by_reference = max($min_date, $max_date);

// $date_by_reference and $max_date are now the same object

echo '$max_date is ' . date_format($max_date, 'Y-m-d') . PHP_EOL; // '2019-03-06'
echo '$date_by_reference is ' . date_format($date_by_reference, 'Y-m-d') . PHP_EOL; // '2019-03-06'

date_add($date_by_reference, date_interval_create_from_date_string('1 days')); // Add 1 day to $date_by_reference, changes $max_date too

echo '$max_date is changed ' . date_format($max_date, 'Y-m-d') . PHP_EOL; // '2019-03-07'
echo '$date_by_reference is changed ' . date_format($date_by_reference, 'Y-m-d') . PHP_EOL; // '2019-03-07'

?>
To Top