sqrt
(PHP 4, PHP 5)
sqrt — 平方根
说明
$arg
)
返回 arg 的平方根。
参数
-
arg -
要处理的参数
返回值
返回 arg 的平方根，负数时返回 NAN。
范例
Example #1 sqrt() 例子
<?php
// Precision depends on your precision directive
echo sqrt ( 9 ); // 3
echo sqrt ( 10 ); // 3.16227766 ...
?> 参见
- pow() - 指数表达式
用户评论:
[#1] justin at hoogs dot com dot au [2015-03-10 04:12:33]
As we all know, the square of the hypotenuse is equal to the sum of the squares of the other two sides of a right triangle (a2 + b2 = c2).
With that in mind I created a quick way to reduce images to a maximum area without messing up width/height constraints.
<?php
list($width_orig, $height_orig) = getimagesize($img);
$max_a = 500000; // maximum area in pixels
$width = $width_orig;
$height = $height_orig;
$area = $width * $height;
if ($area > $max_a) {
$mult = sqrt($max_a) / sqrt($height * $width);
$width *= $mult;
$height *= $mult;
}
?>
[#2] jouhni at web dot de [2005-02-17 11:46:45]
To get any root of a number your can use the pow() function:
pow(8, 1/3)
which gives you the third root of eight.
Jouhni