How to Convert an Octal String to an Integer in PHP?

You can convert an octal string to an integer by using the octdec() function, for example, like so:

var_dump(octdec('30071')); // int(12345)
var_dump(octdec('030071')); // int(12345)
var_dump(octdec('0o30071')); // int(12345) (PHP 8.1+)
var_dump(octdec('0O30071')); // int(12345) (PHP 8.1+)

This works for values prefixed with 0, 0o and 0O, as well as values that don't have any of these prefixes.

For invalid values passed to octdec() (such as non-numeric values), this would show a deprecation message in PHP 7.4+ (and silently ignored in versions prior):

// ...

// Deprecated: Invalid characters passed for attempted conversion, these have been ignored

To support conversion of octal strings with radix prefixes (i.e. 0o or 0O) in versions of PHP before v8.1, you could do something like the following:

// PHP <8.1
function octToDec(string $str): int {
    if (strpos(strtolower($str), '0o') === 0) {
        $str = substr($str, 2);

    return octdec($str);

var_dump(octToDec('30071')); // int(12345)
var_dump(octToDec('030071')); // int(12345)
var_dump(octToDec('0o30071')); // int(12345)
var_dump(octToDec('0O30071')); // int(12345)

This works in the following way:

  1. Strip out 0o (or 0O) octal prefixes, if any;
  2. Call octdec() to convert the octal string to a decimal number and return the resulting integer.

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