9

How can I delete an element from a multi-dimensional array given a key?

I am hoping for this to be greedy so that it deletes all elements in an array that match the keys I pass in. I have this so far where I can traverse a multi-dimensional array but I can't unset the key I need to because I don't have a reference to it!

function traverseArray($array, $keys)
{ 
    foreach($array as $key=>$value)
    { 
        if(is_array($value))
        { 
            traverseArray($value); 

        } else {

            if(in_array($key, $keys))
           {                    
                //unset(what goes here?) 

            }

        } 
    }

}
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1
  • I think Call-time pass-by-reference has been deprecated. Especially since I am using this in a class in Code-igniter. Commented Aug 20, 2011 at 21:45

4 Answers 4

Reset to default
8

The following code works (and doesn't use deprecated stuff), just tested it:

function traverseArray(&$array, $keys) { 
  foreach ($array as $key => &$value) { 
    if (is_array($value)) { 
      traverseArray($value, $keys); 
    } else {
      if (in_array($key, $keys)){
        unset($array[$key]);
      }
    } 
  }
}
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1 Comment

This was very useful, thanks @Marian. If anyone uses this and wants to perform a check on the VALUE of the element you're removing, you can check $value just before performing unset();
1

You could use pass by reference, declare your function like this:

function traverseArray(&$array, $keys)
{ 
    foreach($array as $key=>$value)
    { 
        if(is_array($value))
        { 
            traverseArray($value, $keys); 
        }else{
            if(in_array($key, $keys)){
                unset($array[$key]);
            }
        } 
    }
}

then you can unset the key and it will vanish from the original passed value too since the $array in the function is merely a pointer to the array you passed so it updates that array.

unset($array[$key]);

For more information check the php documentation on passing by reference

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4 Comments

I get this message Call-time pass-by-reference has been deprecated. I am using this in a class in Codeigniter.
I edited my answer to include your whole function. Additionally you need to make sure that when you call it you use traverseArray($array, $keys) and not traverseArray(&$array, $keys)
Right, I don't get that error anymore. However, the array is the same as before. I am wondering can this really work in a class? I am calling the above function from another function in a class and this function isn't returning anything. The way I call it is like so: $this->traverseArray($errors, array('e1', 'e2'));
@Abs Marian Galik beat me to finding the bug and his code works, Andrej L had already figured out that little part of it.
0

You can do this

unset($array[$key]);

because $array will not be a copy of the original array, just a reference to it, so any modifications will hold.

Also, you have a small bug in your snippet: when you make the recursive call, you forget the pass the $keys parameter.

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2 Comments

@sg3s in new versions (php5.x, don't know for sure) it's the default + the pass-by-reference &$var is deprecated. See this answer (stackoverflow.com/questions/6138454/…) for clarification.
I'm quite sure @sg3's right. The & in a function call, like foo(&$a); is deprecated according to the manual, but otherwise it says function foo(&$var) {.
0

and don't forget to modify foreach:

foreach($array as $key=>&$value)
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3 Comments

You don't need to do this once a variable is referenced it will carry it through to all the uses of that variable afaik (someone feel to test this? :p)
You can't change array values in foreach.
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