CODE EXAMPLE FOR PHP

php key_exists

PHP function key_exists($key, array $array) bool
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Checks if the given key or index exists in the array. The name of this function is array_key_exists() in PHP > 4.0.6.

Parameters:
int|string--$key--Value to check.
array--$array--An array with keys to check.
  
Returns:true on success or false on failure.