How to pick what array_intersect function to use in PHP?

October 26, 2018

So you want to do an intersect, but not sure which PHP function to use? There are around 8 variations on the array

intersection function built into PHP. Here is a guide for helping your pick which one to use!

The main array intersect functions in PHP

The basic idea of all of them is that it will return an array of all values from the first array that are also in the

other arrays.

The differences between them are based on the following:

  • If the user provides the compare function (u)
  • If it will compare keys (assoc), values, or both
array_intersect()

This is the main one, I guess!

This will return an array with all values from $array1 that are present in all the others. It just compares the

values, ignoring the keys

array_intersect_assoc()

Same as above, but it checks both values and keys

array_intersect_uassoc()

It checks the keys (via user supplied function) and values. The values are checked by normal comparison, but they keys are checked by a user

supplied function.

array_intersect_key()

Returns array of everything from the first array which have keys in the other arrays.

array_intersect_ukey()

Same as above, but the comparison function for the keys is provided by the user.

array_uintersect()

Same as array_intersect() - but the user provides the comparison function for comparing the values

array_uintersect_assoc()

Same as array_uintersect() (above), but the user provided function checks the keys

array_uintersect_uassoc()

And in this function it is the two above combined. The user provides 2 comparison functions (one for keys, one for values), and it will check

against both of those.

I've been coding professionally for years in PHP, and I still have to double check which one to use every time...