log
A quick addendum to the comment left by "sumeruter": the recursive property will only work if all the sub-arrays are exactly the same length. Otherwise it will just return the longest array every time.
max
(PHP 4, PHP 5)
max — 找出最大值
说明
max() 返回参数中数值最大的值。
如果仅有一个参数且为数组，max() 返回该数组中最大的值。如果第一个参数是整数、字符串或浮点数，则至少需要两个参数而 max() 会返回这些值中最大的一个。可以比较无限多个值。
Note: PHP 会将非数值的 string 当成 0，但如果这个正是最大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 且是最大值，max() 会返回其中数值的 0，如果参数中没有数值的 0，则返回按字母表顺序最大的字符串。
Example #1 使用 max() 的例子
<?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
// 对多个数组，max 从左向右比较。
// 因此在本例中：2 == 2，但 4 < 5
$val = max(array(2, 4, 8), array(2, 5, 7)); // array(2, 5, 7)
// 如果同时给出数组和非数组作为参数，则总是将数组视为
// 最大值返回
$val = max('string', array(2, 5, 7), 42); // array(2, 5, 7)
?>
add a note
User Contributed Notesmax
soapergem at gmail dot com
07-Jul-2009 07:58
07-Jul-2009 07:58
marcini
11-May-2009 02:34
11-May-2009 02:34
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.
sumeruter+php add an at gmail dot com
09-Dec-2008 11:54
09-Dec-2008 11:54
An interesting feature not mentioned is that if a recursive array is passed to max, max will return the sub-array containing the highest value.
Example:
<?php
$depth3=array(
array(array(1,6,3),array(7,2,5),array(9,3,0)),
array(array(2,1,8),array(4,4,5),array( 99 ,6,7)),
array(array(0,3,2),array(5,91,11),array(42,25,12)));
$depth2=max($depth3);
// = array(array(2,1,8),array(4,4,5),array( 99 ,6,7))
$depth1=max($depth2);
// = array( 99 ,6,7)
$depth0=max($depth1);
// = 99
echo max(max(max($depth3)));
// echo 99;
?>
ries at vantwisk dot nl
09-Nov-2008 02:36
09-Nov-2008 02:36
I had several occasions that using max is a lot slower then using a if/then/else construct. Be sure to check this in your routines!
Ries
Marcus Zacco
29-Sep-2008 04:47
29-Sep-2008 04:47
This code loops through seven arrays and finds the highest average value within those arrays - and changes the font color for it. Great for highlighting.
The biggest take-away is this the row
if($average[$i] == max($average))
The number_format just rounds the numbers to 0 decimal points.
<?php
for ( $i = 0; $i <= 6; $i++) {
$num = $i+1;
if($average[$i] == max($average)) {
echo "Value ".$num.": <font color='red'>".number_format($average[$i], 0, '.', '')." % </font<br>";
} else {
echo "Value ".$num.": ".number_format($average[$i],0,'.','')." %<br>";
}
}
?>
### OUTPUT
Value 1: 52 %
Value 2: 58 %
Value 3: 56 %
Value 4: 73 %
Value 5: 77 % <- this 77 is highlighted in red
Value 6: 71 %
Value 7: 75 %
henk at tobbe dot net dot au
16-Apr-2008 07:05
16-Apr-2008 07:05
In a publication by WROX I noted a variant of the earlier "bound" function:
A parameter had to be between 1 and 3...
$par=round((min(max($x,1),3));
stuff at necr0manzer dot de
03-Mar-2008 07:11
03-Mar-2008 07:11
mick at wireframe dot com's solution to finding the key for the highest value didn't work for me, so I wrote one myself:
<?php
function max_key($array) {
foreach ($array as $key => $val) {
if ($val == max($array)) return $key;
}
}
$array = array(1, 2, 5, 7, 4);
echo max($array); // 7
echo max_key($array); // 3
?>
of course this also works with associative arrays, but it will only return a single result!
harmor
21-Feb-2008 05:56
21-Feb-2008 05:56
A way to bound a integer between two values is:
function bound($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
mick at wireframe dot com
30-Oct-2007 11:51
30-Oct-2007 11:51
There are a couple of things you can do for cleaner code if you want the keys returned from the array. I am not sure how they each impact performance, but the visual readability is more beneficial for me -- your mileage may vary.
In the first example keys and max value is returned:
<?php
// First, let's pretend we have an array like this:
$Some_Array = array(
'john' => 40,
'susan' => 40,
'jane' => 24,
'michael' => 19,
'jimmy' => 38
);
function max_extract($My_Array) {
$Max_Value = max($My_Array);
return array_fill_keys(array_keys($My_Array, $Max_Value), $Max_Value);
} // ! max_extract()
?>
Or, if you are only interested in the keys and don't care what the max is:
<?php
function max_extract($My_Array) {
return array_keys($My_Array, max($My_Array));
// You can also array_flip() this is you want them as keys
// or if some other reason makes this relevant/needed.
} // ! max_extract()
?>
There are many possible variations when using the search parameter of array_keys() along with other array functions.
sta
07-Sep-2007 04:05
07-Sep-2007 04:05
Or to take multiple maximum values into consideration:
function doublemax($mylist){
$maxvalue=max($mylist);
$max_keys = array();
while(list($key,$value)=each($mylist)){
if($value==$maxvalue)
array_push($max_keys,$key);
}
return $max_keys;
}
joan dot codina at upf dot edu
14-Jul-2007 05:11
14-Jul-2007 05:11
This is highly ineficient, but can be a bit better
<?
function doublemax($mylist){
$maxvalue=max($mylist);
while(list($key,$value)=each($mylist)){
if($value==$maxvalue)
return array("key"=>$key,"value"=>$value);
}
}
?>
michaelangel0 at mail.com
04-Jul-2007 10:00
04-Jul-2007 10:00
Matlab users and others may feel lonely without the double argument output from min and max functions.
To have the INDEX of the highest value in an array, as well as the value itself, use the following, or a derivative:
<?
function doublemax($mylist){
$maxvalue=max($mylist);
while(list($key,$value)=each($mylist)){
if($value==$maxvalue)$maxindex=$key;
}
return array("m"=>$maxvalue,"i"=>$maxindex);
}
?>
jeremi23 at gmail dot com
14-Jun-2007 10:09
14-Jun-2007 10:09
max on a an array with key/values
<?
$tmp = array(1 => 5, 2=> 3);
echo max($tmp);
?>
this return 5, so the max is done on the values.
johnmott59 at hotmail dot com
17-May-2007 07:35
17-May-2007 07:35
To find the maximum value from a set of 1-dimensional arrays, do this:
$d1 = array(450,420,440,430,421);
$d2 = array(460,410,410,430,413,375,256,411,656);
$d3 = array(430,440,470,435,434,255,198);
$t = max(max($d1),max($d2),max($d3));
// $t is 656
The inner max() functions operate on the arrays, the outer max compares the numeric results of the inner ones.
johnphayes at gmail dot com
02-May-2006 04:27
02-May-2006 04:27
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
tim at (NOSPAM) dot crazynot2 dot com
08-Nov-2005 09:56
08-Nov-2005 09:56
In response to the previous two posters (zher0 at netcarrier dot com & walkingmantis):
I was trying to do exactly what zher0 suggested; calculate the max value of a multi-dimensional array with variably sized 'sub-arrays'. Here is a simple little function I came up with to do just that:
<?php
function multimax( $array ) {
// use foreach to iterate over our input array.
foreach( $array as $value ) {
// check if $value is an array...
if( is_array($value) ) {
// ... $value is an array so recursively pass it into multimax() to
// determine it's highest value.
$subvalue = multimax($value);
// if the returned $subvalue is greater than our current highest value,
// set it as our $return value.
if( $subvalue > $return ) {
$return = $subvalue;
}
} elseif($value > $return) {
// ... $value is not an array so set the return variable if it's greater
// than our highest value so far.
$return = $value;
}
}
// return (what should be) the highest value from any dimension.
return $return;
}
?>
Please note that I have only performed very limited testing on this code -- be sure to check it thoroughly if you implement it somewhere!
nonick AT 8027 DOT org
17-Dec-2003 03:50
17-Dec-2003 03:50
If you are working with numbers, then you can use:
$a = ($b > $c) ? $b : $c;
which is somewhat faster (roughly 16%) than
$a = max($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.
mikhail_kovalev at mail dot ru
13-May-2003 11:32
13-May-2003 11:32
Note that in version 4.0.3 (the only version I tested):
max (0, 0); // returns 0.
max (0, false); // returns 0.
max (false, 0); // returns false.
max (false, false); // returns false.
As a solution use this:
(int) max (false, 0); // returns 0.
(int) max (false, false); // returns 0.