php, efficient way to determine if this value is in my array [duplicate]

Question

Possible Duplicate:
Find values in multidimensional arrays

This is my array, it contains an array of key value pairs.

[
   {
    valueA: 0,
    valueB: 0,
    day: "2010-04-09"
   },
   {
    valueA: 0,
    valueB: 0,
    day: "2010-04-10"
   }
]

I want to check if a certain value is at key "day" in any index (and if so, modify the values in that node)

is there an efficient way to do this with the in_array method?

otherwise I guess I would do it with a nested for loop

Answer 1

Loop only once and set date as key

$hash = array();
foreach ( $array as $v ) {
    $hash[$v['day']][] = $v;
}

Now you can use isset which is O(1) rather than O(n) all the time

if (isset($hash['2010-04-10'])) {
    echo "Here";
}

Answer 2

Not with the in_array function, but you can use array_filter:

// assuming $myarray = Array(......);
if( $found = array_filter($myarray,function($a) {return $a['day'] == '2010-04-10';})) {
    // you can now do something with the $found array
}

EDIT: Just saw your comment about using PHP 5.2.2 - this version doesn't support anonymous functions, so you will need this:

if( $found = array_filter($myarray,create_function('$a','return $a["day"] == "2010-04-10";')))

Answer 3

I would use array_map instead. This will allow you to modify the array when the keys match. array_filter just allows population of an array.

If you create a new method (using 5.2 and create_function) you can specify your logic in it. Then, pass that into the array_map method to get your new, processed array.

In my example below, I'm checking to see if the 'day' of the variable is '2010-04-10' - and if so, changing valueA of that particular array to 1.

$processArrayFunction = create_function('$a',
                                        'if ($a["day"] == "2010-04-10") {
                                            $a["valueA"] = 1;
                                        }
                                        return $a;
                                        ');

$newArray = array_map($processArrayFunction, $sourceArray);