IF statement on MYSQL query - IF all values for a column are the same -

is possible have php if statement saying if values of [column3] same, run code?

i have mysqli query returning values if values column 3 same, want run php code.

thanks, daniel

this query return 1 row 1 column number of different values in column3:

select count(distinct column3) mytable 

if value 1, there's 1 value in column.