Driver Code
$ N = 4 ; $ mat = array ( array ( 1 , 0 , 0 , 0 ) , array ( 0 , 1 , 0 , 0 ) , array ( 0 , 0 , 1 , 0 ) , array ( 0 , 0 , 0 , 1 ) ) ; if ( isIdentity ( $ mat , $ N ) ) echo " Yes ▁ " ; else echo " No ▁ " ; ? >