Check if a key exists and get a corresponding value from an array in PHP

Question

Any idea how to check if a key exists and if yes, then get the value of this key from an array in php.

E.g.

I have this array:

$things = array(
  'AA' => 'American history',
  'AB' => 'American cooking'
);

$key_to_check = 'AB';

Now, I need to check if $key_to_check exists and if it does, get a coresponding value which in this case will be American cooking

Answer 1

if(isset($things[$key_to_check])){
    echo $things[$key_to_check];
}

Answer 2

I know this question is very old but for those who will come here It might be useful to know that in php7 you can use Null Coalesce Operator

if ($value = $things[ $key_to_check ] ?? null) {
      //Your code here
}

Answer 3

if (array_key_exists($key_to_check, $things)) {
    return $things[$key_to_check];
}

Answer 4

isset() will return:
-true if the key exists and the value is != NULL
-false if the key exists and value == NULL
-false if the key does not exist

array_key_exists() will return:
-true if the key exists
-false if the key does not exist

So, if your value may be NULL, the proper way is array_key_exists. If your application doesn't differentiate between NULL and no key, either will work, but array_key_exists always provides more options.

In the following example, no key in the array returns NULL, but so does a value of NULL for a given key. That means it's effectively the same as isset.

The null coalesce operator(??) wasn't added until PHP 7, but this works back to PHP 5, maybe 4:

$value = (array_key_exists($key_to_check, $things) ? $things[$key_to_check] : NULL);

as a function:

function get_from_array($key_to_check, $things)
    return (array_key_exists($key_to_check,$things) ? $things[$key_to_check] : NULL);

Answer 5

The simpliest approach is to do this:

if( isset( $things[ $key_to_check ]) ) {
   $value = $things[ $key_to_check ];
   echo "key {$key_to_check} exists. Value: {$value}";
} else {
   echo "no key {$key_to_check} in array";
}

And you get the value usual way:

$value = $things[ $key_to_check ];

Answer 6

Just use isset(), you can use it as follows if you want to use it as an function:

function get_val($key_to_check, $array){
    if(isset($array[$key_to_check])) {
        return $array[$key_to_check]);
    }
}

Answer 7

For Laravel users, you can use this helper out-of-the-box, thanks to the illuminate/support library:

// use Illuminate\Support\Arr;
Arr::get($array, $key, $default_value)

Which is the equivalent of:

array_key_exists($key, $array) ? $array[$key] : $default_value;

This helper supports the dot notation for keys. Ex: "key1.key2.key3", which is the equivalent of doing $array["key1"]["key2"]["key3"].

Outside Laravel (ex. vanilla PHP), you can manually add this library with composer.

Answer 8

Try this:

$value = @$things[$key_to_check] ?? $default_value;