Using an array (or xml) to program a function - php

Question

Ultimate Goal
Is to make something like Magento offers - basically a logic builder, and as shown by this post on Stackoverflow: jQuery (or any web tool) Nested Expression Builder So far I have made jQuery to build a tree and get the data that I want the builder to use, check, and set. Now I just need to parse the checks and add it into various places in a script I'm making - but I am unsure how to process it dynamically so that these checks can be performed, which will lead to some actions occurring/data being changed automatically.
Maybe we can call this dynamic expression processing?
Original Post
Forgive me, I know what I would like to do, but have little idea how to do it - so I'm looking for some inspiration. I have allowed a multidimensional array to be generated, and the array would contain certain 'commands' and logic functions, and when a condition is true it is executed.
In it's most basic form, the array would contain a set of if statements, where if the statement were true, then would would proceed to the next array item and go down a level, if it were false, then you'd proceed to the next array item with no children (an unmarried sibling, i guess we could call it). Once there is nothing left to process, since nothing is true, then nothing would happen.
I'd imagine that maybe the best way to 'feed' the data in would be via XML - though would this be possible, I mean, to keep going deeper, else go down, essentially until there is a true condition?
Basically, the array takes the following form (though I not 100% sure I've written it correctly, but I think it looks right :s):
[0][0] => array('function' => 'if', 'check' => 'day', 'condition' => 'equals', 'value' => '3');
[0][1][0] => array('function' => 'set', 'name' => 'date_day', 'value' => 'wednesday');
[1][0] => array('function' => 'if', 'check' => 'day', 'condition' => 'equals', 'value' => '4');
[1][1][0] => array('function' => 'set', 'name' => 'date_day', 'value' => 'thursday');
So the above would be - if day=3, then set date_day as wednesday; else if day=4, then set date_day as thursday
Which I'd imagine would correspond to (though i have no idea if you can sub item):
<items>
<item>
<function>if</function>
<check>day</check>
<condition>equals</condition>
<value>3</value>
<item>
<function>set</function>
<name>date_day</name>
<value>wednesday</value>
</item>
</item>
<item>
<function>if</function>
<check>day</check>
<condition>equals</condition>
<value>4</value>
<item>
<function>set</function>
<name>date_day</name>
<value>thursday</value>
</item>
</item>
</items>
Which would basically make the following statements in a function of some sort:
function ($current_data){
LOOP
if(FUNCTION == "if"){
if(CHECK CONDITION VALUE){
**go to next item deeper in the chain**
} else {
**go to sibling item**
}
} else if(FUNCTION == "set"){
define(NAME, VALUE);
}
ENDLOOP
}
I know the above can be done using the date() function, but this is a very basic example. Another example could involve check to see if the colour entered was red, and if it were, then set something based on this colour, else do something else if it were blue. Another could be to set the template to be for US visitors if the US flag was clicked on. The point is that it could basically fulfil any action and do a check and give a result - basically like programming - but where the function data is feed in by PHP or XML
I'm sure there must be something out there that can accomplish this, but I just have no idea were to start exactly, so any assistance would be great - and yes I know there could be some security concerns, but I plan on having checks in place checking that the checks, conditions, values, etc are safe (so this needs to be able to be factored in).
Many many thanks!

Answer 1

Okay JSON vs. XML aside, here's how I would process that array...
$array = xmldecode($xml);
$resultFound = false;
$i = 0;
while(!$resultFound && $i < count($array)) {
if (myFunction($array[$i]) {
$resultFound = true;
}
$i++;
}
if (!$resultFound) {
// error condition
}
function myFunction($array) {
$function = $array[0]['function'];
switch($function) {
case 'if':
$checkVariable = $array[0]['check'];
$condition = $array[0]['condition'];
$checkValue = $array[0]['value'];
switch($checkVariable)
case 'day':
switch($condition) {
case 'equals':
if (GLOBAL_DAY == $checkValue) {
return myFunction($array[1]);
} else {
return false;
}
break;
case 'less than':
if (GLOBAL_DAY < $checkValue) {
return myFunction($array[1]);
} else {
return false;
}
break;
}
break;
}
break;
case 'set':
$setVariable = $array[0]['name'];
$setValue = $array[0]['value'];
switch($setVariable) {
case 'date_day':
GLOBAL_DATE_DAY = $setValue;
return true;
break;
}
break;
}
}

Answer 2

Your problem is very similar to that of form validation, so I would look at some popular jQuery form validation plugins or MVC frameworks like CakePHP. These typically all have stock building blocks for the most common validation rules that the user can easily put together and pass specific arguments to to cover most scenarios.
The notable difference between your problem and these examples is that form validation frameworks are aimed at developers, so they can simply write custom functions if they need to glue multiple rules together to form a more complex rule. However, you can still achieve something that works for probably 98% of all use cases by doing something like:
$offers = array(
'pet feed sale' => array(
'category' => array(1, 2, 3)
'total' => '>100',
'weekday' => array('mon', 'wed')
'set' => array(
'discount' => 80
'shipping' => 0
)
),
'medication sale' => array(
'category' => 4
'date' => '2012-1-28',
'set' => array(
'discount' => 50
)
)
);
And if the user needs apply more complex pricing structures then they could, for instance, break the "pet feed sale" rule into 3 offers, one for dog food, one for cat food, and one for fish food. There might be more repetition, but it makes it much easier to implement than a full parser.
Also, most non-programmers probably handle repetition a lot better than complicated logic and control flow.