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PHP : Function Reference : Mathematical Functions : max

max

Find highest value (PHP 4, PHP 5)
mixed max ( array values )
mixed max ( mixed value1, mixed value2 [, mixed value3...] )

Example 1150. Example uses of 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

// With multiple arrays, max compares from left to right
// so in our example: 2 == 2, but 4 < 5
$val = max(array(2, 4, 8), array(2, 5, 7)); // array(2, 5, 7)

// If both an array and non-array are given, the array
// is always returned as it's seen as the largest
$val = max('string', array(2, 5, 7), 42);   // array(2, 5, 7)
?>

Related Examples ( Source code ) » max
















Code Examples / Notes » max

johnmott59

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.


joan dot codina

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);
 }
}
?>


mick

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.


johnphayes

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


sta

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;
}


mikhail_kovalev

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.


jeremi23

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.


michaelangel0

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);
}
?>


tim

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

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.


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