max

说明

mixed max ( number arg1, number arg2 )

mixed max ( array numbers [, array ...] )

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。

注: 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。如果多个参数的值都是 0，max() 将返回第一个（最左边的值）。

例子 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) ?>

参见 min() 和 count()。

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johnphayes at gmail dot com
03-May-2006 12:27


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 05:56


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 11:50


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
14-May-2003 07:32


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.

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