Converting Python Code to PHP

I created a python-to-php converter called py2php. It can auto-translate the basic logic and then you will need to tweak library calls, etc. Still experimental.

Here is auto-generated PHP from the python provided by the OP.

<?php
require_once('py2phplib.php');
require_once( 'math.php');
function calcNumEntropyBits($s) {
    if ((count($s) <= 0)) {
        return 0.0;
    }
    $symCount = array();
    foreach( $s as $c ) {
        if (!$symCount.__contains__($c)) {
            $symCount[$c] = 1;
        }
        else {
            $symCount[$c] += 1;
        }
    }
    $entropy = 0.0;
    foreach( $symCount->iteritems() as $temp_c ) {
        $prob = ($n / float(count($s)));
        $entropy += ($prob * (math::log($prob) / math::log(2)));
    }
    if (($entropy >= 0.0)) {
        return 0.0;
    }
    else {
        return -($entropy * count($s));
    }
}

function testEntropy($s) {
    pyjslib_printFunc(sprintf('Bits of entropy in \'%s\' is %.2f', new pyjslib_Tuple([$s, calcNumEntropyBits($s)])));
}

testEntropy('hello world');
testEntropy('bubba dubba');
testEntropy('aaaaaaaaaaa');
testEntropy('aaaaabaaaaa');
testEntropy('abcdefghijk');

It would not run correctly due to the math import and __contains__, but those would be easy enough to fix by hand.

I'm not aware of any Python-to-PHP converter in the wild, but it should be a trivial task to port and the similarities are quite easy to spot:

function calcNumEntropyBits($s) {
        if (strlen($s) <= 0) return 0.0;
        $symCount = array();
        foreach (str_split($s) as $c) {
                if (!in_array($c,$symCount)) $symCount[$c] = 1;
                else $symCount[$c] ++;
        }
        $entropy = 0.0;
        foreach ($symCount as $c=>$n) {
                $prob = $n / (float)strlen($s);
                $entropy += $prob * log($prob)/log(2);
        }
        if ($entropy >= 0.0) return 0.0;
        else return -($entropy*strlen($s));
}

function testEntropy($s):
        printf("Bits of entropy in '%s' is %.2f",$s,calcNumEntropyBits($s));

testEntropy('hello world');
testEntropy('bubba dubba');
testEntropy('aaaaaaaaaaa');
testEntropy('aaaaabaaaaa');
testEntropy('abcdefghijk');

The last few lines in the first function could have also been written as a standard PHP ternary expression:

return ($entropy >= 0.0)? 0.0: -($entropy*strlen($s));