Q. PHP program to find whether a number is power of two or not.

Here you will find an algorithm and program in PHP to find whether the given number is power of 2 or not. Now first let us understand what power of two means.

Explanation : In mathematics, a power of two is a number of the form 2^n where n is an integer. Here we use a mathematical concept of Logarithm, The most simple method for finding whether a number is power of two or not is to simply take the log of the number on base 2 and if you get an integer then the number is the power of 2.

For Example : 256, when we take log of 256 to the base 2 we get 8 which is integer, hence 256 is power of 2.

Algorithm to find whether a number is power of two or not

```START
Step 1 → Take integer variable num
Step 2 → find out the log number with base 2
Step 3 → if outcome is integer then DISPLAY number is power of 2.
Step 4 → Otherwise, DISPLAY number is not power of 2.
STOP
```

PHP Program to Find Whether a Given Number is Power of 2

```function Log2(\$x)
{
return (log10(\$x) / log10(2));
}

function find_power_of_two(\$num)
{
return (ceil(Log2(\$num)) ==  floor(Log2(\$num)));
}

\$num=256;
if(find_power_of_two(\$num))
echo "\$num is the power of two";
else
echo "\$num is not the power of two";
```

Output

```256 is the power of two.
```