Question

I’m looking at websites that use php and I seea[]=val1 instead ofb=val2. My question is why are there brackets in the url? What type of code would produce this effect?

Answer 1

Why Are the Brackets in the URL?

The brackets are in the url to indicate that val1 is to be assigned the next position in the array a. If you are confused about the blank part of the bracket, look at how php arrays work.

What Kind of Code Would Produce This?

As for the code that would create such a url, it could either be an explicit definition by the coder or some other script, or it could be somehow created by a form using the method="get" attribute.

Example:

To create this, you can define an array as the name of an input field like so:

<form method="get">
  <input name="a[]" ... />
  <input name="a[]" ... />
  <input name="a[]" ... />
</form>

Or you can just make a link (the a tag) with this url:

<a href="foo.php?a[]=val1&a[]=val2&a[]=val3">Click Me!</a>

To parse this url with PHP, you would use the $_GET variable to retrieve the values from the url:

<?php
  $a = $_GET['a'];

  $val1 = $a[0];
  $val2 = $a[1];
  $val3 = $a[2];
  ...

  print_r($a);
?>

The printout of the print_r($a) statement would look like this (if you wrapped it in a <pre> tag):

Array (
  a => Array (
    0 => 'val1',
    1 => 'val2',
    2 => 'val3'
  )
)