Check if an array contains a specific value?

Question

I'd like to check if there is a value on an array like this:

function check_value_new ($list, $message) {
    foreach ($list as $current) {
        if ($current == $message) return true;
    }
    return false;
}

function check_value_old ($list, $message) {
    for ($i = 0; $i < count ($status_list); $i ++) {
        if ($status_list[$i] == $$message) return true;
    }
    return false;
}

$arr = array ("hello", "good bye", "ciao", "buenas dias", "bon jour");
check_value_old ($arr, "buenas dias"); // works but it isn't the best
check_value_new ($arr, "buenas dias"); // argument error, where I'm wrong?

I've read the check_value_new method is a better way to work with arrays, but I'm not used to work with it, how I should fix it?

Anthony Forloney · Accepted Answer · 2010-02-04T15:29:39.237

PHP offers a function called in_array that checks if a value exists in a given array.

You can change your check_value_new function to include this:

function check_value_new ($list, $message) {
   foreach ($list as $current) {
     if (in_array($message, $current)) {
            return true;
  }
   return false;
}

If you'd like to, you could also make the function work without the foreach loop, like so

function check_value_new ($list, $message) {
  // returns true if found, else returns false.
     return in_array($message, $list); 
 }

score 0 · Answer 2 · answered Mar 04 '21 at 00:00

The reasons that your check_value_old() function breaks is because you have a typo in your loop's second parameter. $status_list is not one of the variables passed into your function and it is not declared anywhere before it is used. You merely need to use $list instead. It is also not necessary to call count() on every iteration -- since that value never changes in the loop, just call it once before the loop and use that value in the second parameter.

As for deciding how to loop over array values, there is no reason to reinvent a native function call. in_array() was already designed and optimized to search linear values in an array and return true as soon as it finds a match; otherwise it returns false.

I don't know what @AnthonyForloney is doing by writing in_array() inside of a foreach() loop. Not only will the snippet break because there aren't enough curly braces, the input array does not have two levels of data, so in_array() will choke when it receives $current which is a string (not the expected array).

Ultimately, my advice is: Only write your own custom function when there isn't a native function to suit your needs. Throw away both of the manual looping ideas and only call:

$arr = ["hello", "good bye", "ciao", "buenas dias", "bon jour"];
var_export(in_array("buenas dias", $arr));

One final insight that I'd like to provide is regarding microoptimization. If you are planning to check the existence of a unique value in a "very large" array, or if you are going to be making thousands of searches on the same array, then it would be more efficient to set up your array in a "flipped" orientation and call isset() or array_key_exists(). isset()/array_key_exists() will always outperform in_array() or array_search() because of the way that php handles arrays as "hash maps". More reading here.

Check if an array contains a specific value?

2 Answers2