To convert a binary number to decimal we have to find the power of each digit of the binary number according to their position which starts from 0 in reverse and add those together. For example if the entered number is 1011 then we calculate (1 × 2³) + (0 × 2²) + (1 × 2¹) + (1 × 2?) which is 11.
In this program, we are using the built-in function bindec() to convert binary to a decimal value. First, we have to accept the binary value from the user and assigning it to the variable bin and we have to create a variable flag with the value true and assign the length of the variable bin to the variable len. Then we have to perform for loop to check whether the entered num is a valid binary number or not first assign the value 0 into the variable i and perform the loop until the condition 'i < len' becomes false and also increment the value of the variable i in every iteration in the block of the loop we have to Check the condition 'bin[i] != 0' and 'bin[i] != 1' if both are true assign the value false to the variable flag and after the completion of the loop we have to Check the value of variable flag if it is true assign the value of built-in function 'bindec(bin)' to the variable dec and print the value of the variable des as the binary equivalent of the variable bin otherwise print the entered number is not a valid binary number
Syntax of function bindec()
bindec(binary_string);
Step 1: Accept the binary number into the variable bin
Step 2: Create a variable with the value true
Step 3: Assign the length of the variable bin to the variable len
Step 4: Perform the for loop to check whether the entered number is a valid binary number or not first assign the value 0 into the variable i and perform the following sub-steps until the condition 'i < len' becomes false and also increment the value of the variable i in every iteration
(i) Check the condition 'bin[i] != 0' and 'bin[i] != 1' if both are true assign the value false to the variable flag
Step 5: Check the value of the variable flag if it is true assign the value of built-in function 'bindec(bin)' to the variable dec and print the value of the variable des as the binary equivalent of the variable bin otherwise print the entered number is not a valid binary number
<?php
$bin = readline("Enter the binary value: ");
$flag = true;
$len = strlen($bin);
for ($i = 0; $i < $len; $i++) {
if ($bin[$i] != 1 && $bin[$i] != 0) {
$flag = false;
}
}
if ($flag) {
$dec = bindec($bin);
echo "Decimal equivalent of $bin is $dec";
} else {
echo "Enter a valid binary number.";
}
?>
Enter the binary value: 100111 Decimal equivalent of 100111 is 39
