The array_flip() function is used to exchange the keys with their associated values in an array. The function returns an array in flip order, i.e. keys from array become values and values from array become keys.
Note: The values of the array need to be valid keys, i.e. they need to be either integer or string. A warning will be emitted if a value has the wrong type, and the key-value pair in question will not be included in the result.
It returns an array in flip order, i.e. keys from input become values and values from input become keys.