In what scenarios should isset() be preferred over in_array() for checking the existence of a value in PHP?

isset() should be preferred over in_array() when you want to specifically check if a key exists in an array, rather than checking if a value exists in an array. isset() is used to determine if a variable is set and is not NULL, while in_array() is used to check if a value exists in an array. 

// Using isset() to check if a key exists in an array
$array = ['key1' => 'value1', 'key2' => 'value2'];

if (isset($array['key1'])) {
    echo 'Key exists in the array';
} else {
    echo 'Key does not exist in the array';
}

Keywords

isset in_array value existence PHP scenarios

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