I want to write a function that take input as a string and convert alphabets to number and returns the converted numbers, in this way: A(a)=1, B(b)=2, C(c)=3... Z(z)=25 using php
thanks in advance
First, we make everything lowercase.
Then, using the ord function, we get the ascii code, and then substract 'a' from it.
function one_char_map($chr)
{
$chr=strtolower($chr);
return ord($chr)-ord('a');
}
function string_map($str)
{
return implode(array_map('one_char_map',str_split($str)));
}
echo string_map('abcD');//0123
Please try this :
function conv($alph=null){
return (!is_null($alph)?strpos("abcdefghijklmnopqrstuvwxyz", $alph):"Need String");
}
echo "<br /><br />";
echo conv("a");
EDIT :
$str = "abcDefghZ";
$out = "";
for($i=0;$i<strlen($str);$i++){
$out .= conv(strtolower($str[$i]));
}
echo $str."<br />".$out;
If you trying to roll your own hash function: DONT.
If you need to accept other characters from ASCII, use PHP's ord() function.
Try this:
This function returns the position, and optionally accepts a base integer to shift the numbers if you need to.
function alpha_ord($str, $base = 0) {
$pos = stripos(
'abcdefghijklmnopqrstuvwxyz',
$str{0}
);
if ($pos !== FALSE) {
$pos += $base;
}
return $pos;
}
print alpha_ord('A'); // 0
print alpha_ord('Z', 1); // 26
print alpha_ord('Z'); // 25
print alpha_ord('A', 65); // 65
I tried to look on here as to why this code is not working, got no where and now I'm hoping someone can help me out.
function validateData($string) {
if (empty($string)) {
return 'error';
} elseif (strlen($string) <= 1) {
return 'error';
} elseif (preg_match('[a-zA-Z0-9]+\ ?', $string)) {
return 'error';
} else {
return 'normal';
}
}
When I execute the above code, using:
echo validateData('Test');
echo validateData('Test!');
These both echo 'normal'.. however, the second example contains the '!' in the string and should return 'error' because of the preg_match statement in the above code.
Achievement Objective. Check a string to make sure that it is not EMPTY, that it is longer than 1 character and only contains a-z, A-Z, 0-9 or a space. So no special characters.
Thank you very much in advance to all answers, I really appreciate it!
Ken
Your pattern should look like this:
preg_match('/([^a-zA-Z0-9 ])+/', $string);
The ^ symbol is used to negate a character set.
use !preg_match(pattern,$string), if you need to validate strings which contains spaces, then use following, otherwise, remove \s from preg_match pattern
function validateData($string) {
if (empty($string)) {
return 'error';
} elseif (strlen($string) <= 1) {
return 'error';
} elseif (!preg_match('/^[A-Za-z0-9\s]+$/', $string)) {
return 'error';
} else {
return 'normal';
}
}
If the string is empty, it will be equal to 0 when you ask for it's string length, therefore testing empty($string) is useless since it is covered by the second test.
Using a regex adds complexity without benefit here, there is a dedicated function to return true or false for alphanumeric string: ctype_alnum($string)
Your function can just be:
function validateData($string) {
return (strlen($string) <= 1 || !ctype_alnum($string)) ? 'error' : 'normal';
}
try:
preg_match('/[a-zA-Z0-9]+\ ?/', $string)
Replace
preg_match('[a-zA-Z0-9]+\ ?', $string)
with
preg_match('/[^a-zA-Z0-9]/', $string)
I have a string and want to test using PHP if it's a valid base64 encoded or not.
I realise that this is an old topic, but using the strict parameter isn't necessarily going to help.
Running base64_decode on a string such as "I am not base 64 encoded" will not return false.
If however you try decoding the string with strict and re-encode it with base64_encode, you can compare the result with the original data to determine if it's a valid bas64 encoded value:
if ( base64_encode(base64_decode($data, true)) === $data){
echo '$data is valid';
} else {
echo '$data is NOT valid';
}
You can use this function:
function is_base64($s)
{
return (bool) preg_match('/^[a-zA-Z0-9\/\r\n+]*={0,2}$/', $s);
}
Just for strings, you could use this function, that checks several base64 properties before returning true:
function is_base64($s){
// Check if there are valid base64 characters
if (!preg_match('/^[a-zA-Z0-9\/\r\n+]*={0,2}$/', $s)) return false;
// Decode the string in strict mode and check the results
$decoded = base64_decode($s, true);
if(false === $decoded) return false;
// Encode the string again
if(base64_encode($decoded) != $s) return false;
return true;
}
This code should work, as the decode function returns FALSE if the string is not valid:
if (base64_decode($mystring, true)) {
// is valid
} else {
// not valid
}
You can read more about the base64_decode function in the documentation.
I think the only way to do that is to do a base64_decode() with the $strict parameter set to true, and see whether it returns false.
I write this method is working perfectly on my projects. When you pass the base64 Image to this method, If it valid return true else return false. Let's try and let me know any wrong. I will edit and learn in the feature.
/**
* #param $str
* #return bool
*/
private function isValid64base($str){
if (base64_decode($str, true) !== false){
return true;
} else {
return false;
}
}
This is a really old question, but I found the following approach to be practically bullet proof. It also takes into account those weird strings with invalid characters that would cause an exception when validating.
public static function isBase64Encoded($str)
{
try
{
$decoded = base64_decode($str, true);
if ( base64_encode($decoded) === $str ) {
return true;
}
else {
return false;
}
}
catch(Exception $e)
{
// If exception is caught, then it is not a base64 encoded string
return false;
}
}
I got the idea from this page and adapted it to PHP.
I tried the following:
base64 decode the string with strict parameter set to true.
base64 encode the result of previous step. if the result is not same as the original string, then original string is not base64 encoded
if the result is same as previous string, then check if the decoded string contains printable characters. I used the php function ctype_print to check for non printable characters. The function returns false if the input string contains one or more non printable characters.
The following code implements the above steps:
public function IsBase64($data) {
$decoded_data = base64_decode($data, true);
$encoded_data = base64_encode($decoded_data);
if ($encoded_data != $data) return false;
else if (!ctype_print($decoded_data)) return false;
return true;
}
The above code will may return unexpected results. For e.g for the string "json" it will return false. "json" may be a valid base64 encoded string since the number of characters it has is a multiple of 4 and all characters are in the allowed range for base64 encoded strings. It seems we must know the range of allowed characters of the original string and then check if the decoded data has those characters.
Alright guys... finally I have found a bullet proof solution for this problem. Use this below function to check if the string is base64 encoded or not -
private function is_base64_encoded($str) {
$decoded_str = base64_decode($str);
$Str1 = preg_replace('/[\x00-\x1F\x7F-\xFF]/', '', $decoded_str);
if ($Str1!=$decoded_str || $Str1 == '') {
return false;
}
return true;
}
if u are doing api calls using js for image/file upload to the back end this might help
function is_base64_string($string) //check base 64 encode
{
// Check if there is no invalid character in string
if (!preg_match('/^(?:[data]{4}:(text|image|application)\/[a-z]*)/', $string)){
return false;
}else{
return true;
}
}
Old topic, but I've found this function and It's working:
function checkBase64Encoded($encodedString) {
$length = strlen($encodedString);
// Check every character.
for ($i = 0; $i < $length; ++$i) {
$c = $encodedString[$i];
if (
($c < '0' || $c > '9')
&& ($c < 'a' || $c > 'z')
&& ($c < 'A' || $c > 'Z')
&& ($c != '+')
&& ($c != '/')
&& ($c != '=')
) {
// Bad character found.
return false;
}
}
// Only good characters found.
return true;
}
I code a solution to validate images checking the sintaxy
$image = 'data:image/png;base64,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';
$allowedExtensions = ['png', 'jpg', 'jpeg'];
// check if the data is empty
if (empty($image)) {
echo "Empty data";
}
// check base64 format
$explode = explode(',', $image);
if(count($explode) !== 2){
echo "This string isn't sintaxed as base64";
}
//https://stackoverflow.com/a/11154248/4830771
if (!preg_match('%^[a-zA-Z0-9/+]*={0,2}$%', $explode[1])) {
echo "This string isn't sintaxed as base64";
}
// check if type is allowed
$format = str_replace(
['data:image/', ';', 'base64'],
['', '', '',],
$explode[0]
);
if (!in_array($format, $allowedExtensions)) {
echo "Image type isn't allowed";
}
echo "This image is base64";
But a safe way is using Intervention
use Intervention\Image\ImageManagerStatic;
try {
ImageManagerStatic::make($value);
return true;
} catch (Exception $e) {
return false;
}
You can just send the string through base64_decode (with $strict set to TRUE), it will return FALSE if the input is invalid.
You can also use f.i. regular expressions see whether the string contains any characters outside the base64 alphabet, and check whether it contains the right amount of padding at the end (= characters). But just using base64_decode is much easier, and there shouldn't be a risk of a malformed string causing any harm.
base64_decode() should return false if your base64 encoded data is not valid.
i know that i resort a very old question, and i tried all of the methods proposed; i finally end up with this regex that cover almost all of my cases:
$decoded = base64_decode($string, true);
if (0 < preg_match('/((?![[:graph:]])(?!\s)(?!\p{L}))./', $decoded, $matched)) return false;
basically i check for every character that is not printable (:graph:) is not a space or tab (\s) and is not a unicode letter (all accent ex: èéùìà etc.)
i still get false positive with this chars: £§° but i never use them in a string and for me is perfectly fine to invalidate them.
I aggregate this check with the function proposed by #merlucin
so the result:
function is_base64($s)
{
// Check if there are valid base64 characters
if (!preg_match('/^[a-zA-Z0-9\/\r\n+]*={0,2}$/', $s)) return false;
// Decode the string in strict mode and check the results
$decoded = base64_decode($s, true);
if(false === $decoded) return false;
// if string returned contains not printable chars
if (0 < preg_match('/((?![[:graph:]])(?!\s)(?!\p{L}))./', $decoded, $matched)) return false;
// Encode the string again
if(base64_encode($decoded) != $s) return false;
return true;
}
MOST ANSWERS HERE ARE NOT RELIABLE
In fact, there is no reliable answer, as many non-base64-encoded text will be readable as base64-encoded, so there's no default way to know for sure.
Further, it's worth noting that base64_decode will decode many invalid strings
For exmaple, and is not valid base64 encoding, but base64_decode WILL decode it. As jw specifically. (I learned this the hard way)
That said, your most reliable method is, if you control the input, to add an identifier to the string after you encode it that is unique and not base64, and include it along with other checks. It's not bullet-proof, but it's a lot more bullet resistant than any other solution I've seen. For example:
function my_base64_encode($string){
$prefix = 'z64ENCODEDz_';
$suffix = '_z64ENCODEDz';
return $prefix . base64_encode($string) . $suffix;
}
function my_base64_decode($string){
$prefix = 'z64ENCODEDz_';
$suffix = '_z64ENCODEDz';
if (substr($string, 0, strlen($prefix)) == $prefix) {
$string = substr($string, strlen($prefix));
}
if (substr($string, (0-(strlen($suffix)))) == $suffix) {
$string = substr($string, 0, (0-(strlen($suffix))));
}
return base64_decode($string);
}
function is_my_base64_encoded($string){
$prefix = 'z64ENCODEDz_';
$suffix = '_z64ENCODEDz';
if (strpos($string, 0, 12) == $prefix && strpos($string, -1, 12) == $suffix && my_base64_encode(my_base64_decode($string)) == $string && strlen($string)%4 == 0){
return true;
} else {
return false;
}
}
I have found my solution by accident.
For those who use base64_encode(base64_decode('xxx')) to check may found that some time it is not able to check for string like test, 5555.
If the invalid base 64 string was base64_decode() without return false, it will be dead when you try to json_encode() anyway. This because the decoded string is invalid.
So, I use this method to check for valid base 64 encoded string.
Here is the code.
/**
* Check if the given string is valid base 64 encoded.
*
* #param string $string The string to check.
* #return bool Return `true` if valid, `false` for otherwise.
*/
function isBase64Encoded($string): bool
{
if (!is_string($string)) {
// if check value is not string.
// base64_decode require this argument to be string, if not then just return `false`.
// don't use type hint because `false` value will be converted to empty string.
return false;
}
$decoded = base64_decode($string, true);
if (false === $decoded) {
return false;
}
if (json_encode([$decoded]) === false) {
return false;
}
return true;
}// isBase64Encoded
And here is tests code.
// each tests value must be 'original string' => 'base 64 encoded string'
$testValues = [
555 => 'NTU1',
5555 => 'NTU1NQ==',
'hello' => 'aGVsbG8=',
'สวัสดี' => '4Liq4Lin4Lix4Liq4LiU4Li1',
'test' => 'dGVzdA==',
];
foreach ($testValues as $invalid => $valid) {
if (isBase64Encoded($invalid) === false) {
echo '<strong>' . $invalid . '</strong> is invalid base 64<br>';
} else {
echo '<strong style="color:red;">Error:</strong>';
echo '<strong>' . $invalid . '</strong> should not be valid base 64<br>';
}
if (isBase64Encoded($valid) === true) {
echo '<strong>' . $valid . '</strong> is valid base 64<br>';
} else {
echo '<strong style="color:red;">Error:</strong>';
echo '<strong>' . $valid . '</strong> should not be invalid base 64<br>';
}
echo '<br>';
}
Tests result:
555 is invalid base 64 NTU1 is valid base 64
5555 is invalid base 64 NTU1NQ== is valid base 64
hello is invalid base 64 aGVsbG8= is valid base 64
สวัสดี is invalid base 64 4Liq4Lin4Lix4Liq4LiU4Li1 is valid base
64
test is invalid base 64 dGVzdA== is valid base 64
To validate without errors that someone sends a clipped base64 or that it is not an image, use this function to check the base64 and then if it is really an image
function check_base64_image($base64) {
try {
if (base64_encode(base64_decode($base64, true)) === $base64) {
$img = imagecreatefromstring(base64_decode($base64, true));
if (!$img) {
return false;
}
imagepng($img, 'tmp.png');
$info = getimagesize('tmp.png');
unlink('tmp.png');
if ($info[0] > 0 && $info[1] > 0 && $info['mime']) {
return true;
}
}
} catch (Exception $ex) {
return false;
} }
I am using this approach. It expects the last 2 characters to be ==
substr($buff, -2, 1) == '=' && substr($buff, -1, 1) == '=')
Update: I ended up doing another check if the one above fails
base64_decode($buff, true)
If data is not valid base64 then function base64_decode($string, true) will return FALSE.
I have an issue here with filter_array.
below is my code:
$array = array("0","0","1");
function returnzero($d){
if($d=='0'){
return $d;
}
}
$all_zeros = array_filter($array, "returnzero");
echo count($all_zeros);
I would like to filter out all values that none other than zero.
Above is my code. However, the count result returned is always 0.
may I know what is my mistake?
Thanks.
See the documentation on array_filter
You need to be returning true or false, not the number... So your function becomes:
function returnzero($d) { return $d == 0; }
You need to check $d != 0 and it will return all the non-zero values. Trying to return 0 is the same as returning false, so it fails.
Function must returns TRUE.
$array = array(0, 0, 1);
function returnzero($d){
if($d=='0'){
return true;
}
}
$all_zeros = array_filter($array, "returnzero");
echo count ($all_zeros);
Modify the return value to reflect the purpose:
function iszero($d) { return $d == '0'; }
$all_zeros = array_filter($array, 'iszero');
Regards
rbo
The function you pass into array_filter() must return TRUE or FALSE to tell PHP whether the current value being checked matches what you're filtering for. You're returning the number that was passed in. Since you're checking for zeroes, you're returning zero, which PHP interprets as FALSE. You could rewrite the function as follows:
if ($d == 0) {
return TRUE;
} else {
return FALSE;
}
or more concisely
return ($d == 0);
I have a viariable that contains something like this ab_123456789
how can i check if the variable starts with ab_?
thanks,
sebastian
Another way using substr:
if (substr('ab_123456789', 0, 3) === 'ab_')
Here substr is used to take the first 3 bytes starting at position 0 as a string that is then compared to 'ab_'. If you want to add case-insensivity, use strcasecmp.
Edit To make the use more comfortable, you could use the following startsWith function:
function startsWith($str, $prefix, $case_sensitivity=false) {
if ($case_sensitivity) {
return substr($str, 0, strlen($prefix)) === $prefix;
} else {
return strcasecmp(substr($str, 0, strlen($prefix)), $prefix) === 0;
}
}
Note that these functions do not support multi-byte characters as only bytes are compared. An equivalent function with multi-byte support could look like this:
function mb_startsWith($str, $prefix, $case_sensitivity=false) {
if ($case_sensitivity) {
return mb_substr($str, 0, mb_strlen($prefix)) === $prefix;
} else {
return mb_strtolower(mb_substr($str, 0, mb_strlen($prefix))) === mb_strtolower($prefix);
}
}
Here the character encoding of both strings is assumed to be the internal character encoding.
Use regular expressions
$var = "ab_123456789";
if(preg_match('/^ab_/', $var, $matches)){
/*your code here*/
}
You can use strpos():
$text = "ab_123456789";
if(strpos($text, "ab_") === 0)
{
// Passed the test
}
The easiest way would be to get a sub string. e.g. substr('ab_123456789', 0, 3);
It's quite easy, as your string can be accessed like an array of characters. So you just have to do something like :
if ($var[0] == "a" && $var[1] == "b" && $var[2] == "c")
return true
You also could use a find function from php library.