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
sqrt
(PHP 4, PHP 5, PHP 7)
sqrt — Quadratwurzel
Beschreibung
float sqrt
( float
$arg
)
Berechnet die Quadratwurzel des Parameters arg.
Parameter-Liste
-
arg -
Der zu verarbeitende Wert
Rückgabewerte
Die Quadratwurzel des Parameters arg
oder der spezielle Wert NAN für negative
Eingabewerte.
Beispiele
Beispiel #1 sqrt() Beispiel
<?php
// Die Anzahl der Nachkommastellen hängt von der 'precision' Einstellung ab
echo sqrt(9); // 3
echo sqrt(10); // 3.16227766 ...
?>
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User Contributed Notes 2 notes
jouhni at web dot de ¶
11 years ago
justin at hoogs dot com dot au ¶
1 year ago
As we all know, the square of the hypotenuse is equal to the sum of the squares of the other two sides of a right triangle (a2 + b2 = c2).
With that in mind I created a quick way to reduce images to a maximum area without messing up width/height constraints.
<?php
list($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;
}
?>
