The identity matrix is a square matrix where all elements of principal diagonals are 1s, and other elements are 0s. In this tutorial, I am giving an identity matrix example using PHP program.

### The below is an example of an Identity matrix:

1 0 0 0 1 0 0 0 1

The above matrix is containing 1s for principal diagonals, and others are 0s.

### Here is a PHP program for displaying an Identity matrix:

<html> <body> <?php echo "<b>The matrix is given below:-</b>"."<br>"; $a=array(array()); for($i=0;$i<3;$i=$i+1) { for($j=0;$j<3;$j=$j+1) { if($i==$j) { $a[$i][$j]=1; } else { $a[$i][$j]=0; } echo $a[$i][$j]." "; } echo "<br>"; } ?> </body> </html>

### Output:

The matrix is given below:- 1 0 0 0 1 0 0 0 1

In the above PHP program, there are three rows and three columns. When row index number is equal to the column index number, then 1s are assigning here as a value to the array elements, and otherwise, 0s are assigning to other array elements.