<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title> max_min.php </title>
<meta charset="UTF-8">
<meta name="Author" content="">
<meta name="Keywords" content="">
<meta name="Description" content="">
</head>
<body>
<form method="post" action="">
<input type="text" name="usrname"><br>
<input type="submit">
</form>
<br>usrname:<br>
<?php
$a=1;
$b=2;
$c=3;
$d=4;
$arr=array(1,2,3,4,5,6,7,8,9);
echo max($a,$b) . '<br>';//2
echo min($a,$b) . '<br>';//1
echo max($a,$b,$c) . '<br>';//3
echo min($a,$b,$c) . '<br>';//1
echo max($a,$b,$c,$d) . '<br>';//4
echo min($a,$b,$c,$d) . '<br>';//1
echo max($arr) . '<br>';//9
echo min($arr) . '<br>';//1
?>
</body>
</html>