Checking if array element is a key

Question

How does one loop through an array and then subsequently check to see if the current selected element is a key? Thanks.

E.g. for the following:

for($i=0;$i<count($arr);$i++) {
  //if($arr[$i]) == key, or typeOf($arr[$i]) == key, then doSomething();
}

what do you mean by "current selected element " and "is a key" — Joseph
– Joseph, Commented Feb 28, 2012 at 10:30
What do you mean by that? Every element in the array consists of a key and value. Do you mean the value is a key in another array? — Felix Kling
– Felix Kling, Commented Feb 28, 2012 at 10:30
edit the question instead of placing the example in a comment — Joseph
– Joseph, Commented Feb 28, 2012 at 10:31
key is not a datatype or anything in PHP (certainly not a keyword). It's still not clear what you want to do. What is key in your example? — Felix Kling
– Felix Kling, Commented Feb 28, 2012 at 10:32

Joseph · Accepted Answer · 2012-06-14 06:43:00Z

2

If you want to check if a key exists in an array, then use array_key_exists()

//check if whatever is $key is a key in $array
if(array_key_exists( $key , $array )){
    //do something because it's a key
} else {
    //key not found. not a key
}

to do the other way around and get key if value exists, use array_search():

$array = array(
    0 => 'blue', 
    1 => 'red', 
    2 => 'green', 
    3 => 'red'
);

$key = array_search('green', $array); // $key = 2;
$key = array_search('red', $array);   // $key = 1;

edited Jun 14, 2012 at 6:43

answered Feb 28, 2012 at 10:34

Joseph

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5 Comments

user784446 Over a year ago

Thanks! I sincerely appreciate your answer! However, an additional trouble is acquiring the actual key itself (e.g. "and"=>"word" - how can I get the string of "and" by this means?). Thanks!

Felix Kling Over a year ago

@user784446: IMO it would be much easier to help you, if you provide an example with the data you have (input) and the result you want to get.

user784446 Over a year ago

I'm trying to loop through an array and test to see if either the key or the value to which it's associated passes a strstr test.

Joseph Over a year ago

if you want to get the value, use a key. in PHP, you can also get the key using the value. updated my answer.

Felix Kling Over a year ago

@user784446: Then use a foreach loop foreach($arr as $key => $value)... it seems to be the same problem than your previous question refers to.

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