max

(PHP 4, PHP 5, PHP 7, PHP 8)

max — Find highest value

Description

max(mixed $value, mixed ...$values): mixed

Alternative signature (not supported with named arguments):

max(array $value_array): mixed

If the first and only parameter is an array, max() returns the highest value in that array. If at least two parameters are provided, max() returns the biggest of these values.

Note:
Values of different types will be compared using the standard comparison rules. For instance, a non-numeric string will be compared to an int as though it were 0, but multiple non-numeric string values will be compared alphanumerically. The actual value returned will be of the original type with no conversion applied.

Caution

Be careful when passing arguments of different types because max() can produce unpredictable results.

Parameters

value: Any comparable value.
values: Any comparable values.
value_array: An array containing the values.

Return Values

max() returns the parameter value considered "highest" according to standard comparisons. If multiple values of different types evaluate as equal (e.g. 0 and 'abc') the first provided to the function will be returned.

Errors/Exceptions

If an empty array is passed, max() throws a ValueError.

Changelog

Version	Description
8.0.0	max() throws a ValueError on failure now; previously, `false` was returned and an `E_WARNING` error was emitted.
8.0.0	As string to number comparisons were changed, max() no longer returns a different value based on the argument order in those cases.

Examples

Example #1 Example uses of max()

<?php
echo max(2, 3, 1, 6, 7), PHP_EOL;  / 7
echo max(array(2, 4, 5)), PHP_EOL; / 5

/ Here we are comparing -1 < 0, so 'hello' is the highest value
echo max('hello', -1), PHP_EOL;    / hello

/ With multiple arrays of different lengths, max returns the longest
$val = max(array(2, 2, 2), array(1, 1, 1, 1)); / array(1, 1, 1, 1)
var_dump($val);

/ Multiple arrays of the same length are compared from left to right
/ so in our example: 2 == 2, but 5 > 4
$val = max(array(2, 4, 8), array(2, 5, 1)); / array(2, 5, 1)
var_dump($val);

/ If both an array and non-array are given, the array will be returned
/ as comparisons treat arrays as greater than any other value
$val = max('string', array(2, 5, 7), 42);   / array(2, 5, 7)
var_dump($val);

/ If one argument is NULL or a boolean, it will be compared against
/ other values using the rule FALSE < TRUE regardless of the other types involved
/ In the below example, -10 is treated as TRUE in the comparison
$val = max(-10, FALSE); / -10
var_dump($val);

/ 0, on the other hand, is treated as FALSE, so is "lower than" TRUE
$val = max(0, TRUE); / TRUE
var_dump($val);
?>

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User Contributed Notes 12 notes

down

keith at bifugi dot com ¶

8 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
?>

down

Samu ¶

1 year ago

With modern PHP versions supporting the array spread operator for function arguments, it's tempting to call max() like this:

<?php
function stuff(): iterable {
    / This function might yield 0, 1 or n values.
}

$foo = max(...stuff());
?>

However, this is dangerous if you cannot guarantee that your generator yields **minimum** two values.

The gotcha here is that when max() receives a single argument, it must be an array of values. (When the generator doesn't yield any values, max() will throw an ArgumentCountError.)

If you can guarantee that your generator yields at least one value, then it's safe to call max by relying on the aforementioned array expectation:

<?php
function stuff(): iterable {
    / This function will yield 1...n values.
}

/ Note that here the generator is first read into an array.
$foo = max([...stuff()]);
?>

If the array is empty, max() will throw a ValueError.

The added burden is that faulty code could appear to appear to function just fine but fails at random, probably causing a lot of head-scratching at first.

down

deoomen ¶

2 years ago

Watch out after PHP 8.0!

Sample code:

<?php
echo max(0,'hello');
?>

Before PHP 8.0 will return int(0) but since PHP 8.0 above code returns string("hello")!!

down

volch5 at gmail dot com ¶

11 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

down

Alex Rath ¶

15 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

?>

down

costinu ¶

13 years ago

max(null, 0) = null

max(0, null) = 0

down

johnphayes at gmail dot com ¶

19 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

down

ries at vantwisk dot nl ¶

16 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

down

marcini ¶

16 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.

down

info at osworx dot net ¶

6 years 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

down

blackmac01 at gmail dot com ¶

5 years 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.

down

michaelangel0 at mail.com ¶

17 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);

}

?>

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max

Description

Parameters

Return Values

Errors/Exceptions

Changelog

Examples

See Also

Found A Problem?

User Contributed Notes 12 notes