When would you use the operator '+', in relation to arrays in PHP?

The operator '+' in relation to arrays in PHP is used to create a union of two arrays. When you use this operator, it combines the elements of the first array with the elements of the second array. If there are common keys between the two arrays, the values from the first array are preserved, while the values from the second array are ignored.

This behavior is particularly useful when you want to merge two arrays while maintaining the uniqueness of keys from the first array. The outcome reflects a combination of the two sets of data without losing the information from the first array, unless a key is not present in the second array.

Understanding this operator is crucial for effective data manipulation in PHP, especially when merging datasets or when you want to ensure that existing data within the first array is retained while potentially augmenting it with new data.