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();
}

Answer 1

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;