How can I check if a key exists? If yes, then how do I 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 $key_to_check exists and if it does, get a corresponding value, which in this case will be American cooking.
if(isset($things[$key_to_check])){
echo $things[$key_to_check];
}
It might be useful to know that in PHP 7, you can use the null coalescing operator:
if ($value = $things[ $key_to_check ] ?? null) {
// Your code here
}
$value if it is set and you do not want to check the array twice. However I'll prefer using false instead of null as I think it shows better that we will not run the code inside the if statement then.
$value of 0, false, or empty string. Should do !== null. I would write as two lines: $value = $things[ $key ] ?? null; if ($value !== null) { ... }. (This assumes null is never stored as a value. If do store nulls in array, have to use array_key_exists as seen in other answers.)if (array_key_exists($key_to_check, $things)) {
return $things[$key_to_check];
}
isset would return false if the value is null even though the key actually existsisset() 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);
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 the usual way:
$value = $things[ $key_to_check ];
For Laravel users, you can use this helper out-of-the-box, thanks to the illuminate/support library:
// use Illuminate\Support\Arr;
Arr::get($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 $array["key1"]["key2"]["key3"].
Outside Laravel (ex. vanilla PHP), you can manually add this library with composer.
Just use isset(). You can use it as follows if you want to use it as a function:
function get_val($key_to_check, $array) {
if(isset($array[$key_to_check])) {
return $array[$key_to_check]);
}
}
array_get($things, $key_to_check, 'optional default value');laravel.com/docs/5.1/helpers#method-array-get