PHP Convert variable names to lowercase? - php

Question

I have an api listener script which takes in get parameters. But I seem to be having issues when users tend to pass mixed case variable names on the parameters.
For example:
http://mylistenerurl.com?paramName1=Hello&paramname2=World
I need my listener to be flixible in such a way that the variable names will be interpreted case-insensitively or rather still all in lower case like after I process the query string on some function, they are all returned as lower-cased variables:
extract(someFunction($_GET));
process($paramname1, $paramname2);
Can anybody shed some light on this?
*much appreciated. thanks!

Answer 1

This should do the trick:
$array_of_lower_case_strings = array_map( "strtolower", array( "This Will Be ALL lowercase.", ... ) );
So in your case:
$get_with_lowercase_keys = array_combine(
array_map( "strtolower", array_keys( $_GET ) ),
array_values( $_GET )
);
One thing I'll mention is you should be VERY careful with extract as it could be exploited to allow unexpected variables to be injected into your PHP.

Answer 2

Apply to your global variables ($_GET, $_POST) when necessary:
e.g. setLowerCaseVars($_GET); in your case
function setLowerCaseVars(&$global_var) {
foreach ($global_var as $key => &$value) {
if (!isset($global_var[strtolower($key)])) {
$global_var[strtolower($key)] = $value;
}
}
}
Edit: Note that I prefer this to using array_combine because it will not overwrite cases where the lower-case variable is already set.

Answer 3

PHP has had a native function (array_change_key_case()) for this task since version 4.2 to change the case of first level keys. To be perfectly explicit -- this function can be used to convert first level key to uppercase or lower case BUT this is not a recursive function so deeper keys will not be effected.
Code: (Demo)
parse_str('paramName1=Hello&paramname2=World&fOo[bAR][BanG]=boom', $_GET);
var_export($_GET);
echo "\n---\n";
$lower = array_change_key_case($_GET);
var_export($lower);
Output:
array (
'paramName1' => 'Hello',
'paramname2' => 'World',
'fOo' =>
array (
'bAR' =>
array (
'BanG' => 'boom',
),
),
)
---
array (
'paramname1' => 'Hello', # N changed to n
'paramname2' => 'World',
'foo' => # O changed to o
array (
'bAR' => # AR not changed because not a first level key
array (
'BanG' => 'boom', # B and G not changed because not a first level key
),
),
)