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
?>
max
(PHP 4, PHP 5, PHP 7, PHP 8)
max — Trova il valore massimo
Descrizione
max() restituisce il numericamente più grande dei valori dati come parametro.
Se il primo ed unico parametro è un array, max() restituisce il massimo dei valori di tale array. Se il primo parametro è un integer, string o double, si ha bisogno almeno di due parametri e max() restituisce il maggiore di tali valori. Si può confrontare un numero illimitato di valori.
Nota:
Le stringhe non numeriche saranno considerate dal PHP come
0, ma verrà restituita la stringa se questa è il più alto valore numerico. Se vi sono più argomenti considerati come0, la funzione max() restituirà il primo (il valore più a sinistra).
Example #1 Esempio di max()
<?php
echo max(1, 3, 5, 6, 7); // 7
echo max(array(2, 4, 5)); // 5
echo max(0, 'hello'); // 0
echo max('hello', 0); // hello
echo max(-1, 'hello'); // hello
// Con diversi array, max confronta da sinistra a destra
// quindi nell'esempio: 2 == 2, e 4 < 5
$val = max(array(2, 4, 8), array(2, 5, 7)); // array(2, 5, 7)
// Nel caso siano forniti array e parametri non array, la funzione restituirà
// sempre l'array, considerando questo il più grande
$val = max('string', array(2, 5, 7), 42); // array(2, 5, 7)
?>
add a note
User Contributed Notes 20 notes
keith at bifugi dot com ¶
8 years ago
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.
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")!!
volch5 at gmail dot com ¶
10 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
Alex Rath ¶
14 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
?>
johnphayes at gmail dot com ¶
18 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
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
ReVo_ ¶
10 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
marcini ¶
15 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.
info at osworx dot net ¶
5 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
php at rijkvanwel dot nl ¶
13 years ago
To get the largest key in an array:
<?php
$array = array( 0 => 'first', 1=> 'second', /* ... */ 99 => 'nth' );
$max_key = max( array_keys( $array ) ); // 99
?>
michaelangel0 at mail.com ¶
17 years ago
Matlab users and others may feel lonely without the double argument output from min and max functions.
To have the INDEX of the highest value in an array, as well as the value itself, use the following, or a derivative:
<?php
function doublemax($mylist){
$maxvalue=max($mylist);
while(list($key,$value)=each($mylist)){
if($value==$maxvalue)$maxindex=$key;
}
return array("m"=>$maxvalue,"i"=>$maxindex);
}
?>
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.
sun at drupal dot org ¶
13 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.
harmor ¶
16 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
levim at php dot net ¶
12 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 $max;
}
?>
- This function is not actually recursive, but fulfills the requirement that it works on sub-arrays. I do this because PHP is not very good at recursion. I also did it because I enjoy doing things this way.
- It returns something of type int, never a string representation of an int. The exception is when you provide an array that does not contain any integers. It will then return NULL.
- It ignores non-array, non-int values.
toon dot baeyens at gmail dot com ¶
12 years ago
A little function for multi-dimensional arrays:
<?php
function amax($array){
if(is_array($array)){
foreach($array as $key => $value){
$array[$key] = amax($value);
}
return max($array);
}else{
return $array;
}
}
?>
chris at candm dt org dt uk ¶
3 years ago
A function to return the key of the max value of an array. For multiple max values, it will return the key of first. Change > to >= to get the last.
function array_max_key($arr) {
$maxkey='';
$maxval=false;
array_walk($arr,
function (&$cval,&$ckey) use(&$maxkey,&$maxval) {
if ($maxval === false || $cval > $maxval) {
$maxval = $cval;
$maxkey = $ckey;
}
}
);
return $maxkey;
}
Michael Blinn ¶
5 years 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'
?>
