array_flip() returns an array in flip
order, i.e. keys from
trans become values and values
trans become keys.
Note that the values of
trans 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
If a value has several occurrences, the latest key will be used as its values, and all others will be lost.
array_flip() returns FALSE if it fails.