How to resize image in PHP?

Question

I often see some websites using the below code to resize image size.

?w=250
?w=150
?w=75 
?w=50

Sample:

http://domain.com/customthumb/2013/08/07/72/getty380.jpg?w=250
http://domain.com/customthumb/2013/08/07/72/getty380.jpg?w=150
http://domain.com/customthumb/2013/08/07/72/getty380.jpg?w=75
http://domain.com/customthumb/2013/08/07/72/getty380.jpg?w=50

I already search in Google, but I can't find the solution.

Do you know how to do it in PHP?

---

This is the demo:

Original size don't using "?w=75" or other size: _http://images.detik.com/customthumb/2013/08/09/722/uang4depan.jpg

width 75px : _http://images.detik.com/customthumb/2013/08/09/722/uang4depan.jpg?w=75

width 100px : _http://images.detik.com/customthumb/2013/08/09/722/uang4depan.jpg?w=100

width 110px : _http://images.detik.com/customthumb/2013/08/09/722/uang4depan.jpg?w=110

width 150px : _http://images.detik.com/customthumb/2013/08/09/722/uang4depan.jpg?w=150

Note: remove underscore "_" in front of URL.

Answer 1

I don't know what those URLS are for, but many PHP users use the Imagick functions to manipulate images.

Answer 2

There are several ways, considering what's your output.
First of all, HTML can do this so if you use

print "<img src='...whatever...' width='$x'>"

this will do the trick. Now if you're writing with a header like image/jpg, which means you're being called from an IMG tag and your script returns the image itself - well, use GD library and imagecopyresampled(). But that's a thing I'll explain in detail only if you really need it.