PHP How to Convert Decimal to Binary with Example

In PHP, you can convert a decimal number to binary using the built-in function decbin(), for example, decbin(10) returns 1010.

Examples

Input10

Output1010

Input0

Output0

Input255

Output11111111

How to Think About It

To convert a decimal number to binary, think about dividing the number by 2 repeatedly and recording the remainder each time. These remainders, read in reverse order, form the binary number. PHP's decbin() function does this automatically for you.

Algorithm

1

Get the decimal number as input.

2

Use the built-in function to convert it to binary.

3

Return or print the binary string.

Code

php

<?php
$decimal = 10;
$binary = decbin($decimal);
echo "Binary of $decimal is $binary";
?>

Output

Binary of 10 is 1010

Dry Run

Let's trace the conversion of decimal 10 to binary using decbin()

1

Input decimal number

decimal = 10

2

Call decbin function

binary = decbin(10) // returns '1010'

3

Output binary string

Print 'Binary of 10 is 1010'

Decimal	Binary
10	1010

Why This Works

Step 1: Using decbin()

The decbin() function converts a decimal number to its binary string representation automatically.

Step 2: Input and output

You provide the decimal number as input, and it returns a string of 0s and 1s representing the binary form.

Step 3: Printing result

You can print or use the binary string as needed in your program.

Alternative Approaches

Manual division method

php

<?php
function decimalToBinary($decimal) {
    $binary = '';
    if ($decimal == 0) return '0';
    while ($decimal > 0) {
        $binary = ($decimal % 2) . $binary;
        $decimal = intdiv($decimal, 2);
    }
    return $binary;
}

echo decimalToBinary(10); // outputs 1010
?>

This method shows the logic behind conversion but is longer and less efficient than using decbin().

Complexity: O(log n) time, O(log n) space

Time Complexity

The conversion depends on the number of bits in the decimal number, which is proportional to log base 2 of the number.

Space Complexity

The output string length grows with the number of bits, so space is also proportional to log base 2 of the input.

Which Approach is Fastest?

Using the built-in decbin() is fastest and most optimized compared to manual methods.

Approach	Time	Space	Best For
decbin() built-in	O(log n)	O(log n)	Quick and easy conversion
Manual division	O(log n)	O(log n)	Learning and understanding logic