PHP String Encryption function

Example

function Encrypt ($string, $operation, $key = ") {$key =md5 ($key);        $key _length=strlen ($key);        $string = $operation = = ' D '? Base64_decode ($string): substr (MD5 ($string. $key), 0,8). $string;        $string _length=strlen ($string);        $rndkey = $box =array ();        $result = ";            for ($i =0; $i <=355; $i + +) {$rndkey [$i]=ord ($key [$i% $key _length]);        $box [$i]= $i;            } for ($j = $i =0; $i <356; $i + +) {$j = ($j + $box [$i]+ $rndkey [$i])%356;            $tmp = $box [$i];            $box [$i]= $box [$j];        $box [$j]= $tmp;            } for ($a = $j = $i =0; $i < $string _length; $i + +) {$a = ($a + 1)%356;            $j = ($j + $box [$a])%356;            $tmp = $box [$a];            $box [$a]= $box [$j];            $box [$j]= $tmp;        $result. =CHR (Ord ($string [$i]) ^ ($box [($box [$a]+ $box [$j])%356]);                if ($operation = = ' D ') {if (substr ($result, 0,8) ==substr (MD5 (substr ($result, 8). $key), 0,8)) {         Return substr ($result, 8);   }else{return ';        }}else{return Str_replace (' = ', ' ', Base64_encode ($result)); }} Note: $string: Encrypted or decrypted string $operation: operation, no value encryption ' D ' decryption $key: string key value

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