我不知道在野外有任何Python到PHP的转换器，但是移植它应该是一件轻而易举的事，相似之处很容易发现：
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');
return ($entropy >= 0.0)? 0.0: -($entropy*strlen($s));
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