Saving image as jpg in php issue [duplicate] - javascript

I want to create exact 5 random characters string with least possibility of getting duplicated. What would be the best way to do it? Thanks.

$rand = substr(md5(microtime()),rand(0,26),5);
Would be my best guess--Unless you're looking for special characters, too:
$seed = str_split('abcdefghijklmnopqrstuvwxyz'
.'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
.'0123456789!##$%^&*()'); // and any other characters
shuffle($seed); // probably optional since array_is randomized; this may be redundant
$rand = '';
foreach (array_rand($seed, 5) as $k) $rand .= $seed[$k];
Example
And, for one based on the clock (fewer collisions since it's incremental):
function incrementalHash($len = 5){
$charset = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
$base = strlen($charset);
$result = '';
$now = explode(' ', microtime())[1];
while ($now >= $base){
$i = $now % $base;
$result = $charset[$i] . $result;
$now /= $base;
}
return substr($result, -5);
}
Note: incremental means easier to guess; If you're using this as a salt or a verification token, don't. A salt (now) of "WCWyb" means 5 seconds from now it's "WCWyg")

If for loops are on short supply, here's what I like to use:
$s = substr(str_shuffle(str_repeat("0123456789abcdefghijklmnopqrstuvwxyz", 5)), 0, 5);

You can try it simply like this:
$length = 5;
$randomletter = substr(str_shuffle("abcdefghijklmnopqrstuvwxyz"), 0, $length);
more details: http://forum.arnlweb.com/viewtopic.php?f=7&t=25

A speedy way is to use the most volatile characters of the uniqid function.
For example:
$rand = substr(uniqid('', true), -5);

The following should provide the least chance of duplication (you might want to replace mt_rand() with a better random number source e.g. from /dev/*random or from GUIDs):
<?php
$characters = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
$result = '';
for ($i = 0; $i < 5; $i++)
$result .= $characters[mt_rand(0, 61)];
?>
EDIT:
If you are concerned about security, really, do not use rand() or mt_rand(), and verify that your random data device is actually a device generating random data, not a regular file or something predictable like /dev/zero. mt_rand() considered harmful:
https://spideroak.com/blog/20121205114003-exploit-information-leaks-in-random-numbers-from-python-ruby-and-php
EDIT:
If you have OpenSSL support in PHP, you could use openssl_random_pseudo_bytes():
<?php
$length = 5;
$randomBytes = openssl_random_pseudo_bytes($length);
$characters = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
$charactersLength = strlen($characters);
$result = '';
for ($i = 0; $i < $length; $i++)
$result .= $characters[ord($randomBytes[$i]) % $charactersLength];
?>

I always use the same function for this, usually to generate passwords. It's easy to use and useful.
function randPass($length, $strength=8) {
$vowels = 'aeuy';
$consonants = 'bdghjmnpqrstvz';
if ($strength >= 1) {
$consonants .= 'BDGHJLMNPQRSTVWXZ';
}
if ($strength >= 2) {
$vowels .= "AEUY";
}
if ($strength >= 4) {
$consonants .= '23456789';
}
if ($strength >= 8) {
$consonants .= '##$%';
}
$password = '';
$alt = time() % 2;
for ($i = 0; $i < $length; $i++) {
if ($alt == 1) {
$password .= $consonants[(rand() % strlen($consonants))];
$alt = 0;
} else {
$password .= $vowels[(rand() % strlen($vowels))];
$alt = 1;
}
}
return $password;
}

It seems like str_shuffle would be a good use for this.
Seed the shuffle with whichever characters you want.
$my_rand_strng = substr(str_shuffle("ABCDEFGHIJKLMNOPQRSTUVWXYZ"), -5);

I also did not know how to do this until I thought of using PHP array's. And I am pretty sure this is the simplest way of generating a random string or number with array's. The code:
function randstr ($len=10, $abc="aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStTuUvVwWxXyYzZ0123456789") {
$letters = str_split($abc);
$str = "";
for ($i=0; $i<=$len; $i++) {
$str .= $letters[rand(0, count($letters)-1)];
};
return $str;
};
You can use this function like this
randstr(20) // returns a random 20 letter string
// Or like this
randstr(5, abc) // returns a random 5 letter string using the letters "abc"

$str = '';
$str_len = 8;
for($i = 0, $i < $str_len; $i++){
//97 is ascii code for 'a' and 122 is ascii code for z
$str .= chr(rand(97, 122));
}
return $str

Similar to Brad Christie's answer, but using sha1 alrorithm for characters 0-9a-zA-Z and prefixed with a random value :
$str = substr(sha1(mt_rand() . microtime()), mt_rand(0,35), 5);
But if you have set a defined (allowed) characters :
$validChars = array('0','1','2' /*...*/,'?','-','_','a','b','c' /*...*/);
$validCharsCount = count($validChars);
$str = '';
for ($i=0; $i<5; $i++) {
$str .= $validChars[rand(0,$validCharsCount - 1)];
}
** UPDATE **
As Archimedix pointed out, this will not guarantee to return a "least possibility of getting duplicated" as the number of combination is low for the given character range. You will either need to increase the number of characters, or allow extra (special) characters in the string. The first solution would be preferable, I think, in your case.

If it's fine that you'll get only letters A-F, then here's my solution:
str_pad(dechex(mt_rand(0, 0xFFFFF)), 5, '0', STR_PAD_LEFT);
I believe that using hash functions is an overkill for such a simple task as generating a sequence of random hexadecimal digits. dechex + mt_rand will do the same job, but without unnecessary cryptographic work. str_pad guarantees 5-character length of the output string (if the random number is less than 0x10000).
Duplicate probability depends on mt_rand's reliability. Mersenne Twister is known for high-quality randomness, so it should fit the task well.

works fine in PHP (php 5.4.4)
$seed = str_split('abcdefghijklmnopqrstuvwxyz');
$rand = array_rand($seed, 5);
$convert = array_map(function($n){
global $seed;
return $seed[$n];
},$rand);
$var = implode('',$convert);
echo $var;
Live Demo

Source: PHP Function that Generates Random Characters
This simple PHP function worked for me:
function cvf_ps_generate_random_code($length=10) {
$string = '';
// You can define your own characters here.
$characters = "23456789ABCDEFHJKLMNPRTVWXYZabcdefghijklmnopqrstuvwxyz";
for ($p = 0; $p < $length; $p++) {
$string .= $characters[mt_rand(0, strlen($characters)-1)];
}
return $string;
}
Usage:
echo cvf_ps_generate_random_code(5);

Here are my random 5 cents ...
$random=function($a, $b) {
return(
substr(str_shuffle(('\\`)/|#'.
password_hash(mt_rand(0,999999),
PASSWORD_DEFAULT).'!*^&~(')),
$a, $b)
);
};
echo($random(0,5));
PHP's new password_hash() (* >= PHP 5.5) function is doing the job for generation of decently long set of uppercase and lowercase characters and numbers.
Two concat. strings before and after password_hash within $random function are suitable for change.
Paramteres for $random() *($a,$b) are actually substr() parameters. :)
NOTE: this doesn't need to be a function, it can be normal variable as well .. as one nasty singleliner, like this:
$random=(substr(str_shuffle(('\\`)/|#'.password_hash(mt_rand(0,999999), PASSWORD_DEFAULT).'!*^&~(')), 0, 5));
echo($random);

function CaracteresAleatorios( $Tamanno, $Opciones) {
$Opciones = empty($Opciones) ? array(0, 1, 2) : $Opciones;
$Tamanno = empty($Tamanno) ? 16 : $Tamanno;
$Caracteres=array("0123456789","abcdefghijklmnopqrstuvwxyz","ABCDEFGHIJKLMNOPQRSTUVWXYZ");
$Caracteres= implode("",array_intersect_key($Caracteres, array_flip($Opciones)));
$CantidadCaracteres=strlen($Caracteres)-1;
$CaracteresAleatorios='';
for ($k = 0; $k < $Tamanno; $k++) {
$CaracteresAleatorios.=$Caracteres[rand(0, $CantidadCaracteres)];
}
return $CaracteresAleatorios;
}

I`ve aways use this:
<?php function fRand($len) {
$str = '';
$a = "abcdefghijklmnopqrstuvwxyz0123456789";
$b = str_split($a);
for ($i=1; $i <= $len ; $i++) {
$str .= $b[rand(0,strlen($a)-1)];
}
return $str;
} ?>
When you call it, sets the lenght of string.
<?php echo fRand([LENGHT]); ?>
You can also change the possible characters in the string $a.

Simple one liner which includes special characters:
echo implode("", array_map(function() {return chr(mt_rand(33,126));}, array_fill(0,5,null)));
Basically, it fills an array with length 5 with null values and replaces each value with a random symbol from the ascii-range and as the last, it joins them together t a string.
Use the 2nd array_fill parameter to control the length.
It uses the ASCII Table range of 33 to 126 which includes the following characters:
!"#$%&'()*+,-./0123456789:;<=>?#ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~

Related

Decrypt Crypto-js encrypted text with key with PHP

I'm using Crypto-js for encrypting password with a key and send it to server. I want to decrypt it in server using PHP. How this can be done?
JS:
let encKey = "Secret Passphrase";
let text = "123";
let iv = CryptoJS.enc.Hex.parse("FgLFXEr1MZl2mEnk");
var encryptedText = CryptoJS.AES.encrypt(text, encKey, { iv: iv }).toString();
Encrypted text:
U2FsdGVkX1+EaW3J1GE1k/EU5h6C+nxBH364Xhez+b0=
PHP:
<?php
$strg = "U2FsdGVkX1+EaW3J1GE1k/EU5h6C+nxBH364Xhez+b0=";
$encryptedstrings = base64_decode($strg);
$encryptionMethod = 'aes-256-cbc';
$key = "Secret Passphrase";
$iv = "FgLFXEr1MZl2mEnk";
$rawText = openssl_decrypt($encryptedstrings, $encryptionMethod, $key, OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING , $iv);
var_dump($rawText);
Result:
string(32) "����>���s��ȡ�V?E��M���I"
I'm getting weird results here.
The following solution is not from my side but from #Artjom B., so all credits go to him. You will find the source here: https://stackoverflow.com/a/27678978/8166854.
To your problem: you run the CryptoJs encryption with a passphrase and not with a key. According to the docs (https://cryptojs.gitbook.io/docs/#the-cipher-algorithms) section cipher algorithms the (internal AES) key is derived from the passphrase with an outdated and unsecure function that should no longer be in use.
Artjom B. was able to make this key derivation available on PHP. As a side note: it is not necessary to present an
initialization vector (IV) to the encryption function as the IV is as well derived from the passphrase, so I'm leaving it
out in the following code.
This is the result on PHP-side:
solution for https://stackoverflow.com/questions/65234428/decrypt-crypto-js-encrypted-text-with-key-with-php
string(3) "123"
decryptedtext: 123
This is the code, please obey the warning:
This code is provided for achieve compatibility between different programming languages. It is not necessarily fully secure. Its security depends on the complexity and length of the password, because of only one iteration and the use of MD5. I would recommend to use at least a 20 character password with alphanumeric characters which is ideally randomly generated.
<?php
/*
source: https://stackoverflow.com/a/27678978/8166854 author: Artjom B.
Security notice: This code is provided for achieve compatibility between different programming languages.
It is not necessarily fully secure. Its security depends on the complexity and length of the password,
because of only one iteration and the use of MD5. I would recommend to use at least a 20 character password
with alphanumeric characters which is ideally randomly generated.
*/
function evpKDF($password, $salt, $keySize = 8, $ivSize = 4, $iterations = 1, $hashAlgorithm = "md5") {
$targetKeySize = $keySize + $ivSize;
$derivedBytes = "";
$numberOfDerivedWords = 0;
$block = NULL;
$hasher = hash_init($hashAlgorithm);
while ($numberOfDerivedWords < $targetKeySize) {
if ($block != NULL) {
hash_update($hasher, $block);
}
hash_update($hasher, $password);
hash_update($hasher, $salt);
$block = hash_final($hasher, TRUE);
$hasher = hash_init($hashAlgorithm);
// Iterations
for ($i = 1; $i < $iterations; $i++) {
hash_update($hasher, $block);
$block = hash_final($hasher, TRUE);
$hasher = hash_init($hashAlgorithm);
}
$derivedBytes .= substr($block, 0, min(strlen($block), ($targetKeySize - $numberOfDerivedWords) * 4));
$numberOfDerivedWords += strlen($block)/4;
}
return array(
"key" => substr($derivedBytes, 0, $keySize * 4),
"iv" => substr($derivedBytes, $keySize * 4, $ivSize * 4)
);
}
function decrypt($ciphertext, $password) {
$ciphertext = base64_decode($ciphertext);
if (substr($ciphertext, 0, 8) != "Salted__") {
return false;
}
$salt = substr($ciphertext, 8, 8);
$keyAndIV = evpKDF($password, $salt);
$decryptPassword = openssl_decrypt(
substr($ciphertext, 16),
"aes-256-cbc",
$keyAndIV["key"],
OPENSSL_RAW_DATA, // base64 was already decoded
$keyAndIV["iv"]);
return $decryptPassword;
}
echo 'solution for https://stackoverflow.com/questions/65234428/decrypt-crypto-js-encrypted-text-with-key-with-php' . PHP_EOL;
$key = "Secret Passphrase";
$strg = "U2FsdGVkX1+EaW3J1GE1k/EU5h6C+nxBH364Xhez+b0=";
$rawText = decrypt($strg, $key);
var_dump($rawText);
echo 'decryptedtext: ' . $rawText . PHP_EOL;
?>

Problem with data types. Trying to rewrite js class into php [duplicate]

In PHP, how do I convert:
$result = "abdcef";
into an array that's:
$result[0] = a;
$result[1] = b;
$result[2] = c;
$result[3] = d;
Edited
You will want to use str_split().
$result = str_split('abcdef');
http://us2.php.net/manual/en/function.str-split.php
Don't know if you're aware of this already, but you may not need to do anything (depending on what you're trying to do).
$string = "abcdef";
echo $string[1];
//Outputs "b"
So you can access it like an array without any faffing if you just need something simple.
You can use the str_split() function:
$value = "abcdef";
$array = str_split($value);
If you wish to divide the string into array values of different amounts you can specify the second parameter:
$array = str_split($value, 2);
The above will split your string into an array in chunks of two.
$result = "abcdef";
$result = str_split($result);
There is also an optional parameter on the str_split function to split into chunks of x characters.
best you should go for "str_split()", if there is need to manual Or basic programming,
$string = "abcdef";
$resultArr = [];
$strLength = strlen($string);
for ($i = 0; $i < $strLength; $i++) {
$resultArr[$i] = $string[$i];
}
print_r($resultArr);
Output:
Array
(
[0] => a
[1] => b
[2] => c
[3] => d
[4] => e
[5] => f
)
https://www.php.net/manual/en/function.str-split.php#refsect1-function.str-split-notes
str_split() will split into bytes, rather than characters when dealing with a multi-byte encoded string.
Use mb_str_split() instead.
If you need multibyte support in an outdated version of PHP (a version below PHP7.4), then use preg_split() on an empty pattern with a unicode flag. There is no need to slow down the regex engine with a capture group.
Code: (Demo)
var_export(
preg_split('//u', 'abcåäö', 0, PREG_SPLIT_NO_EMPTY)
// or preg_split('/.\K/us', 'abcåäö', 0, PREG_SPLIT_NO_EMPTY)
// or preg_split('/\X\K/u', 'abcåäö', 0, PREG_SPLIT_NO_EMPTY)
);
For any versions of PHP from 7.4 or higher, just use the dedicated function mb_str_split().
mb_str_split('abcåäö')
Output:
array (
0 => 'a',
1 => 'b',
2 => 'c',
3 => 'å',
4 => 'ä',
5 => 'ö',
)
As a warning to researchers using other answers on this page, if you use square brace syntax to access characters by their offset or you use str_split(), you will get broken results when dealing with multibyte characters.
For anyone doing thorough research, I should also mention the \X (unicode version of the dot) respects newline characters by default. \X is slightly different from . without the s modifier. Demo
var_export(preg_split('/.\K/u', "å\nä", 0, PREG_SPLIT_NO_EMPTY)); // element [1] has two characters in it!
echo "\n---\n";
var_export(preg_split('/.\K/us', "å\nä", 0, PREG_SPLIT_NO_EMPTY));
echo "\n---\n";
var_export(preg_split('/\X\K/u', "å\nä", 0, PREG_SPLIT_NO_EMPTY));
With the help of str_split function, you will do it.
Like below::
<?php
$result = str_split('abcdef',1);
echo "<pre>";
print_r($result);
?>
You can use the str_split() function
$array = str_split($string);
foreach ($array as $p){
echo $p . "<br />";
}
str_split() is not safe for multibyte characters.
mb_str_split() requires PHP 7.4+.
Try preg_split() for the rescuse:
$result = preg_split('/(.)/u', 'abcåäö', -1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);
If you tried the above ways and did not get results, try the following method. It worked for my language (Persian and Arabic):
$result = [];
for ( $i = 0; $i < mb_strlen( $string ); ++ $i ) {
$result[] = mb_substr( $string, $i, 1, 'UTF-8' );
}
var_dump($result);

Is there a way to trim a string formula taken from JSON object and apply it using PHP variables? [duplicate]

I want to calculate math expression from a string. I have read that the solution to this is to use eval(). But when I try to run the following code:
<?php
$ma ="2+10";
$p = eval($ma);
print $p;
?>
It gives me the following error:
Parse error: syntax error, unexpected $end in
C:\xampp\htdocs\eclipseWorkspaceWebDev\MandatoryHandinSite\tester.php(4)
: eval()'d code on line 1
Does someone know the solution to this problem.
While I don't suggest using eval for this (it is not the solution), the problem is that eval expects complete lines of code, not just fragments.
$ma ="2+10";
$p = eval('return '.$ma.';');
print $p;
Should do what you want.
A better solution would be to write a tokenizer/parser for your math expression. Here's a very simple regex-based one to give you an example:
$ma = "2+10";
if(preg_match('/(\d+)(?:\s*)([\+\-\*\/])(?:\s*)(\d+)/', $ma, $matches) !== FALSE){
$operator = $matches[2];
switch($operator){
case '+':
$p = $matches[1] + $matches[3];
break;
case '-':
$p = $matches[1] - $matches[3];
break;
case '*':
$p = $matches[1] * $matches[3];
break;
case '/':
$p = $matches[1] / $matches[3];
break;
}
echo $p;
}
Take a look at this..
I use this in an accounting system where you can write math expressions in amount input fields..
Examples
$Cal = new Field_calculate();
$result = $Cal->calculate('5+7'); // 12
$result = $Cal->calculate('(5+9)*5'); // 70
$result = $Cal->calculate('(10.2+0.5*(2-0.4))*2+(2.1*4)'); // 30.4
Code
class Field_calculate {
const PATTERN = '/(?:\-?\d+(?:\.?\d+)?[\+\-\*\/])+\-?\d+(?:\.?\d+)?/';
const PARENTHESIS_DEPTH = 10;
public function calculate($input){
if(strpos($input, '+') != null || strpos($input, '-') != null || strpos($input, '/') != null || strpos($input, '*') != null){
// Remove white spaces and invalid math chars
$input = str_replace(',', '.', $input);
$input = preg_replace('[^0-9\.\+\-\*\/\(\)]', '', $input);
// Calculate each of the parenthesis from the top
$i = 0;
while(strpos($input, '(') || strpos($input, ')')){
$input = preg_replace_callback('/\(([^\(\)]+)\)/', 'self::callback', $input);
$i++;
if($i > self::PARENTHESIS_DEPTH){
break;
}
}
// Calculate the result
if(preg_match(self::PATTERN, $input, $match)){
return $this->compute($match[0]);
}
// To handle the special case of expressions surrounded by global parenthesis like "(1+1)"
if(is_numeric($input)){
return $input;
}
return 0;
}
return $input;
}
private function compute($input){
$compute = create_function('', 'return '.$input.';');
return 0 + $compute();
}
private function callback($input){
if(is_numeric($input[1])){
return $input[1];
}
elseif(preg_match(self::PATTERN, $input[1], $match)){
return $this->compute($match[0]);
}
return 0;
}
}
I recently created a PHP package that provides a math_eval helper function. It does exactly what you need, without the need to use the potentially unsafe eval function.
You just pass in the string version of the mathematical expression and it returns the result.
$two = math_eval('1 + 1');
$three = math_eval('5 - 2');
$ten = math_eval('2 * 5');
$four = math_eval('8 / 2');
You can also pass in variables, which will be substituted if needed.
$ten = math_eval('a + b', ['a' => 7, 'b' => 3]);
$fifteen = math_eval('x * y', ['x' => 3, 'y' => 5]);
Link: https://github.com/langleyfoxall/math_eval
Using eval function is very dangerous when you can't control the string argument.
Try Matex for safe Mathematical formulas calculation.
Solved!
<?php
function evalmath($equation)
{
$result = 0;
// sanitize imput
$equation = preg_replace("/[^a-z0-9+\-.*\/()%]/","",$equation);
// convert alphabet to $variabel
$equation = preg_replace("/([a-z])+/i", "\$$0", $equation);
// convert percentages to decimal
$equation = preg_replace("/([+-])([0-9]{1})(%)/","*(1\$1.0\$2)",$equation);
$equation = preg_replace("/([+-])([0-9]+)(%)/","*(1\$1.\$2)",$equation);
$equation = preg_replace("/([0-9]{1})(%)/",".0\$1",$equation);
$equation = preg_replace("/([0-9]+)(%)/",".\$1",$equation);
if ( $equation != "" ){
$result = #eval("return " . $equation . ";" );
}
if ($result == null) {
throw new Exception("Unable to calculate equation");
}
echo $result;
// return $equation;
}
$a = 2;
$b = 3;
$c = 5;
$f1 = "a*b+c";
$f1 = str_replace("a", $a, $f1);
$f1 = str_replace("b", $b, $f1);
$f1 = str_replace("c", $c, $f1);
evalmath($f1);
/*if ( $equation != "" ){
$result = #eval("return " . $equation . ";" );
}
if ($result == null) {
throw new Exception("Unable to calculate equation");
}
echo $result;*/
?>
This method has two major drawbacks:
Security, php script is being evaluated by the eval function. This is bad,
especially when the user wants to inject malicious code.
Complexity
I created this, check it out: Formula Interpreter
How does it work ?
First, create an instance of FormulaInterpreter with the formula and its parameters
$formulaInterpreter = new FormulaInterpreter("x + y", ["x" => 10, "y" => 20]);
Use the execute() method to interpret the formula. It will return the result:
echo $formulaInterpreter->execute();
in a single line
echo (new FormulaInterpreter("x + y", ["x" => 10, "y" => 20]))->execute();
Examples
# Formula: speed = distance / time
$speed = (new FormulaInterpreter("distance/time", ["distance" => 338, "time" => 5]))->execute() ;
echo $speed;
#Venezuela night overtime (ordinary_work_day in hours): (normal_salary * days_in_a_work_month)/ordinary_work_day
$parameters = ["normal_salary" => 21000, "days_in_a_work_month" => 30, "ordinary_work_day" => 8];
$venezuelaLOTTTArt118NightOvertime = (new FormulaInterpreter("(normal_salary/days_in_a_work_month)/ordinary_work_day", $parameters))->execute();
echo $venezuelaLOTTTArt118NightOvertime;
#cicle area
$cicleArea = (new FormulaInterpreter("3.1416*(radio*radio)", ["radio" => 10]))->execute();
echo $cicleArea;
About the formulas
It must contain at least two operands and an operator.
Operands' name could be in upper or lower case.
By now, math functions as sin, cos, pow… are not included. I'm working to include them.
If your formula is not valid, you will get an error message like: Error, your formula (single_variable) is not valid.
Parameters' values must be numeric.
You can improve it if you want to!
eval Evaluates the given code as PHP. Meaning that it will execute the given paremeter as a PHP piece of code.
To correct your code, use this :
$ma ="print (2+10);";
eval($ma);
Using eval function
protected function getStringArthmeticOperation($value, $deduct)
{
if($value > 0){
$operator = '-';
}else{
$operator = '+';
}
$mathStr = '$value $operator $deduct';
eval("\$mathStr = \"$mathStr\";");
$userAvailableUl = eval('return '.$mathStr.';');
return $userAvailableUl;
}
$this->getStringArthmeticOperation(3, 1); //2
Finding a sweetspot between the dangers of eval and the limitless calculation possibilities I suggest checking the input for only numbers, operators and brackets:
if (preg_match('/^[0-9\+\-\*\/\(\)\.]+$/', $mathString)) {
$value = eval('return
' . $mathString . ';');
} else {
throw new \Exception('Invalid calc() value: ' . $mathString);
}
It's still easy to use yet relatively save. And it can handle any basic math calulation like (10*(1+0,2)) which isn't possible with most of the mentioned solutions here.
An eval'd expression should end with ";"
Try this :
$ma ="2+10;";
$p = eval($ma);
print $p;
By the way, this is out of scope but the 'eval' function won't return the value of the expression. eval('2+10') won't return 12.
If you want it to return 12, you should eval('return 2+10;');

Trying to convert PHP assignment to Javascript

I am trying to convert a PHP function to javascript, but i cant read the following line of codes:
$sha_string .= "$key=$value$ipn_passphrase";
and
$sha_sign = strtoupper(hash("sha512", $sha_string));
Complete function:
function digistore_signature( $ipn_passphrase, $array)
{
unset($array[ 'sha_sign' ]);
$keys = array_keys($array);
sort($keys);
$sha_string = "";
foreach ($keys as $key)
{
$value = html_entity_decode( $array[ $key ] );
$is_empty = !isset($value) || $value === "" || $value === false;
if ($is_empty)
{
continue;
}
$sha_string .= "$key=$value$ipn_passphrase";
}
$sha_sign = strtoupper(hash("sha512", $sha_string));
return $sha_sign;
}
the $array is the body of a POST request.
the $passphrase is a string
.= in PHP is a simple concatenation. it is similar to the programming concept of +=. It's easy to understand with an example
<?php
$a = "hello";
$a .= " "; //now $a = "hello "
$a .= "world"; // now $a = "hello world"
"$key=$value$ipn_passphrase"; is called an in-place variable substitution in PHP. You can check the PHP Doc for more. You can simply consider it as the value $key, $values and $ipn_passphrase is replaced by the values of those variables accordingly and it forms a new string variable $sha_sign.
$sha_sign = strtoupper(hash("sha512", $sha_string)); is a simple statement where you pass the algorithm sha512 and $sha_string to the function hash() and store the result back in $sha_string variable.

Algorithm to generate small but valid variable names for Javascript in PHP

I am working on a component framework in PHP that generates Javascript from server side and render it on client. Furthermore in Ajax communication the ids and value of components is transfered from client side to server. These ids are meaningful and large in length.
I would like to replace these bigs ids/variables with smaller names like _, _1, _2,_a, or _A So i need an algorithm that can generate next valid Javascript variable name such that whenever i call get_next_id function it gives me next unique variable name. Currently I checked uniqid in PHP but value returned is quite big.
Is there any way or algorithm to generate these type of names in PHP? Please note that the function must fisrt start from smallest possible variable name and then to higher order.
You can increment alphabetic characters in php:
for( $x = 'a'; $x!='z'; $x++) {
echo "$x\n";
}
I believe something like the class below may do the trick. One could easily extend it to use more characters. I've used only lower case characters for simplicity.
class IdGenerator {
function IdGenerator() {
$this->id = 0;
}
function getId() {
$ret = $this->getStringForId($this->id);
$this->id += 1;
return $ret;
}
function getStringForId($id) {
$res = '';
do {
$res = chr( ord('a') + ($id % 26) ) . $res;
$id = (int)($id / 26) - 1;
} while ($id >= 0);
return '_' . $res;
}
}
The class just keeps a simple counter of how many ids it has generated so far. The function getStringForId generates a unique, minimal string for each index it is given.
If you run this test
$g = new IdGenerator();
for ($i = 0; $i < 30; $i++) {
echo $g->getId() . "\n";
}
You'll get
_a
_b
_c
...
_y
_z
_aa
_ab
_ac
_ad

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