Effectively dealing with x quantity $_POST vars - php

Question

I have a piece of code that I'm not happy with at all:
// Search for checkboxes ('chk-1','chk-2','chk-3'...)
foreach ($_POST as $key => $val) {
if (substr($key, 0,3) == 'chk') {
$appObj->cats[] = intval(substr($key,4,strlen($key)));
}
I really don't like this as $_POST can contain upwards of 40+ variables and I am already applying logic to all other posted vars.
Has anyone got any ideas / solutions to achieving the above without cycling through every $_POST var?

Answer 1

The only way how you could avoid cycling trough all items and using strncmp, strpos or substr is building check-boxes as one array (lets have $key = 7 as example):
<input type="checkbox" name="chk[7]" />
And php:
foreach( $_POST['chk'] as $key => $val){
$appObj->cats[] = $key;
}
This would would, but it may create key gaping:
$_POST['chk'] = array(
0 => 'ON',
1 => 'ON',
7 => 'ON',
);
Which may cause problems when someone will try processing data with for loop.
Better approach is this one:
<input type="checkbox" name="chk[]" value="7" />
<input type="checkbox" name="chk[]" value="57" />
<input type="checkbox" name="chk[]" value="1231" />
And php:
foreach( $_POST['chk'] as $arrayKey => $key){
$appObj->cats[] = $key;
}

Answer 2

Try to use name="chk[]" in form control.
<input type="checkbox" name="chk[]" value="1"> 1<br />
<input type="checkbox" name="chk[]" value="2"> 2<br />
<input type="checkbox" name="chk[]" value="3"> 3<br />
And then check if you have an array.
if( !empty($_POST["chk"]) )
{
print_r($_POST["chk"]);
}

Answer 3

Running a foreach through $_POST is really not a crime and is probably the only way to do this.
If you are already appyling other logic why not put this all in the same foreach?
Also to save you some processing you don't need to pass strlen($key) as the 3rd paramater in substr just exclude that parameter completely and it will do the same thing.