The "octdec()" function converts a octal number to decimal number.

 octdec(oct_number)

In the above syntax, "oct_number" is the octal number to be converted to decimal number.

    <?php
    echo octdec(12) . "\n";
    echo octdec(17);
    ?>

    10
    15

In the above example, the octal numbers "12", "17" are converted to decimal numbers "10", "15".