I'm writing a function in php to check, if all arguments are set. This is for preventing the program to crash when a argument isn't set.
Unfortunately I get this error:
Notice: Undefined variable: _POST
The code running is the following:
# check for the right arguments
function checkArguments($type, $arg_array) {
# $type is either 'GET' or 'POST'
# $arg_array is an array with all the arguments names
foreach($arg_array as $arg) {
print(${"_" . $type}["name"]);
$type = "_" . $type;
if(!isset($$type[$arg])) {
$missing[] = $arg;
}
}
}
HI I will assume you wanted a variable variable, I try to avoid them as they are very hard to read in code. It also breaks ( or doesn't work in ) most IDE editors.
One thing I just saw that is relevant.
http://php.net/manual/en/language.variables.variable.php
Please note that variable variables cannot be used with PHP's Superglobal arrays within functions or class methods. The variable $this is also a special variable that cannot be referenced dynamically.
The $_POST would be counted among the "Superglobal" as is $_GET
You could assign them to a temporary variable and use that.
$arr = $_GET;
if ($type == "POST") $arr = $_POST;
Related
I am trying to write a function to avoid getting variable undefined error. Right now, i have a code like this:
function check($str){
if(isset($str)){
$s = $str;
} else {
$s = "";
}
}
check($_GET['var']);
The get var is not set. I am getting a variable undefined error on my screen. How do i alter my function to not throw this error and just return "" if it is not set? I don't want to have to code 100 if statements to avoid getting variable undefined. Thanks.
We already have in PHP a construct to check that. It is called isset(). With it you can check whether a variable exists. If you would like to create it with some default values if it doesn't exist yet, we also have syntax for it. It's null-coalescing operator.
$_GET['var'] = $_GET['var'] ?? '';
// or since PHP 7.4
$_GET['var'] ??= '';
Although I'm not sure if it is the right way of doing it, for the sake of providing an answer you can pass the variable by reference, this allows you to get away with passing undefined variables and check if it is set inside the function..
function check(&$str){
if(!isset($str)){
$str = "not set";
}
}
check($_GET['var']);
echo $_GET['var'];
I have an interesting situation. I am using a form that is included on multiple pages (for simplicity and to reduce duplication) and this form in some areas is populated with values from a DB. However, not all of these values will always be present. For instance, I could be doing something to the effect of:
<?php echo set_value('first_name', $first_name); ?>
and this would work fine where the values exist, but $user is not always set, since they may be typing their name in for the first time. Yes you can do isset($first_name) && $first_name inside an if statement (shorthand or regular)
I am trying to write a helper function to check if a variable isset and if it's not null. I would ideally like to do something like varIsset('first_name'), where first_name is an actual variable name $first_name and the function would take in the string, turn it into the intended variable $first_name and check if it's set and not null. If it passes the requirements, then return that variables value (in this case 'test'). If it doesn't pass the requirements, meaining it's not set or is null, then the function would return '{blank}'.
I am using CodeIgniter if that helps, will be switching to Laravel in the somewhat near future. Any help is appreciated. Here is what I've put together so far, but to no avail.
function varIsset($var = '')
{
foreach (get_defined_vars() as $val) {
if ($val == $var) {
if (isset($val) && $val) {
echo $val;
}
break;
}
}
die;
}
Here is an example usage:
<?php
if (varIsset('user_id') == 100) {
// do something
}
?>
I would use arrays and check for array keys myself (or initialize all my variables...), but for your function you could use something like:
function varIsset($var)
{
global $$var;
return isset($$var) && !empty($$var);
}
Check out the manual on variable variables. You need to use global $$var; to get around the scope problem, so it's a bit of a nasty solution. See a working example here.
Edit: If you need the value returned, you could do something like:
function valueVar($var)
{
global $$var;
return (isset($$var) && !empty($$var)) ? $$var : NULL;
}
But to be honest, using variables like that when they might or might not exist seems a bit wrong to me.
It would be a better approach to introduce a context in which you want to search, e.g.:
function varIsset($name, array $context)
{
return !empty($context[$name]);
}
The context is then populated with your database results before rendering takes place. Btw, empty() has a small caveat with the string value "0"; in those cases it might be a better approach to use this logic:
return isset($context[$name]) && strlen($name);
Try:
<?php
function varIsset($string){
global $$string;
return empty($$string) ? 0 : 1;
}
$what = 'good';
echo 'what:'.varIsset('what').'; now:'.varIsset('now');
?>
I'm writing my own debug functions and I need some help to fix the code below.
I'm trying to print a variable and its name, the file where the variable and the function was declared and the line of the function call. The first part I did, the variable, the variable name, the file and the line is printed correctly.
At the code, a($variable) works good.
The problem is I'd like this function accepts a string too, out of a variable. But PHP returns with a fatal error (PHP Fatal error: Only variables can be passed by reference in ...). At the code, a('text out').
So, how can I fix this code to accept a variable or a string correctly?
code (edited):
function a(&$var){
$backtrace = debug_backtrace();
$call = array_shift($backtrace);
$line = $call['line'];
$file = $call['file'];
echo name($var)."<br>".$var."<br>".$line."<br>".$file;
}
$variable='text in';
a($variable);
a('text out');
I need pass the variable by reference to use this function below (the function get the variable name correctly, works with arrays too):
function name(&$var, $scope=false, $prefix='unique', $suffix='value'){
if($scope) $vals = $scope;
else $vals = $GLOBALS;
$old = $var;
$var = $new = $prefix.rand().$suffix;
$vname = FALSE;
foreach($vals as $key => $val) {
if($val === $new) $vname = $key;
}
$var = $old;
return $vname;
}
The way your code is currently implementing pass by reference is perfect by design, but also by design cannot be changed to have two a() methods - one accepting a variable by reference and the other as a string-literal.
If the desire to pass a string literal instead of assigning it to a variable first is really needed, I would suggest creating a second convenience method named a_str() that actually accepts a string-literal instead of a variable by reference. This method's sole-purpose would be to relay the variable(s) to the original a() method - thereby declaring a variable to pass by reference.
function a_str($var) {
a($var);
}
The only thing to remember is, use a($variable); when passing by reference and a_str('some text'); when not.
Here is the same convenience-method for your name() function:
function name_str($var, $scope=false, $prefix='unique', $suffix='value'){
return name($var, $scope, $prefix, $suffix);
}
The only way to do what you are asking without writing an additional function like #newfurniturey suggests is plain and simply opening and parsing the file where your function was called as text (e.g. with fopen), using the data from debug_backtrace. This will be expensive in terms of performance, but it might be ok if used only for debugging purposes; and using this method you will no longer need a reference in your function, which means you can freely accept a literal as the parameter.
I was trying to pass a variable that contained the name of the superglobal array I wanted a function to process, but I couldn't get it to work, it would just claim the variable in question didn't exist and return null.
I've simplified my test case down to the following code:
function accessSession ($sessName)
{
var_dump ($$sessName);
}
$sessName = '_SERVER';
var_dump ($$sessName);
accessSession ($sessName);
The var_dump outside of the function returns the contents of $_SERVER, as expected. However, the var_dump in the function triggers the error mentioned above.
Adding global $_SERVER to the function didn't make the error go away, but assigning $_SERVER to another variable and making that variable global did work (see below)
function accessSession ($sessName)
{
global $test;
var_dump ($$sessName);
}
$test = $_SERVER;
$sessName = 'test';
var_dump ($$sessName);
accessSession ($sessName);
Is this a PHP bug, or am I just doing something wrong?
PHP: Variable variables - Manual
Warning
Please note that variable variables cannot be used with PHP's Superglobal arrays within functions or class methods. The variable $this is also a special variable that cannot be referenced dynamically.
Solutions
function access_global_v1 ($var) {
global $$var;
var_dump ($$var);
}
function access_global_v2 ($var) {
var_dump ($GLOBALS[$var]);
}
$test = 123;
access_global_v1 ('_SERVER');
access_global_v2 ('test');
From php.net:
Warning
Please note that variable variables cannot be used with PHP's
Superglobal arrays within functions or class methods. The variable
$this is also a special variable that cannot be referenced
dynamically.
The answer is fairly simple: never use variable variables.
Use arrays instead.
(and yes - you are doing something wrong. No, it is not a bug in PHP.)
Use $GLOBALS. There you go :)
<?php
function accessSession ($sessName)
{
var_dump ($GLOBALS[$sessName]);
}
$sessName = '_SERVER';
accessSession ($sessName);
I'm building a small abstract class that's supposed to make certain tasks easier.
For example:
$var = class::get('id');
would run check if there's pointer id in the $_GET, returning a string or array according to parameters. This should also work for post and request and maby more.
I'm doing it in the way there's function for all the superglobals. I'm using get as example:
get function gets a pointer as parameter, it calls fetchdata function and uses the pointer and "$_GET" as the parameters.
fetchdata is supposed to just blindly use the string it got as superglobal and point to it with the other param. Then check if it exists there and return either the value or false to get function, that returns the value/false to caller.
Only problem is to get the string work as superglobal when you don't know what it is. I did this before with a switch that checked the param and in case it was "get", it set $_GET to value of another variable. However I don't want to do it like that, I want it to be easy to add more functions without having to touch the fetchdata.
I tried $method = eval($method), but it didn't work. ($method = "$_GET"), any suggestions?
EDIT: Sorry if I didn't put it clear enough. I have a variable X with string value "$_GET", how can I make it so X gets values from the source described in the string?
So simply it's
$X = $_GET if X has value "$_GET"
$X = $_POST if X has value "$_POST"
I just don't know what value X has, but it needs to get data from superglobal with the same name than its value.
According to this page in the manual:
Note: Variable variables
Superglobals cannot be used as variable variables inside functions or class methods.
This means you can't do this inside a function or method (which you would be able to do with other variables) :
$var = '_GET';
${$var}[$key]
Instead of passing a string to fetchdata(), could you not pass $_GET itself? I think PHP will not copy a variable unless you modify it ('copy on write'), so this shouldn't use memory unnecessarily.
Otherwise there are only nine superglobals, so a switch-case as you have suggested isn't unreasonable.
You could do this with eval() if you really had to, something like:
eval('return $_GET;');
I think that would be unnecessary and a bad idea though; it is slow and you need to be extremely careful about letting untrusted strings anywhere near it.
Don't use eval. Just use reference.
//test value for cli
$_GET['test'] = 'test';
/**
* #link http://php.net/manual/en/filter.constants.php reuse the filter constants
*/
function superglobalValue($key, $input = null) {
if ($input === INPUT_POST)
$X = &$_POST;
else
$X = &$_GET;
return (isset($X[$key]) ? $X[$key] : false);
}
function getArrayValue(&$array, $key) {
return (array_key_exists($key, $array) ? $array[$key] : false);
}
//test dump
var_dump(
superglobalValue('test', INPUT_GET),
superglobalValue('test', INPUT_POST),
getArrayValue($_GET, 'test'),
getArrayValue($_POST, 'test')
);
$_GET, $_POST and $_REQUEST dont have any null values by default, only string or array. So I used isset there instead of array_key_exists.
Param order: I always put required params before optional when I can, and the data objects before the manipulation/subjective params. Thats why key is first param for superglobalValue and second param for getArrayValue.
I'm not quite sure what you're trying to achieve, but you could have a look at the __callStatic magic method
class example{
protected static $supers = array('GET', 'POST', 'SERVER', 'COOKIE');
public static function __callStatic($functionName, $arguments){
$index = arguments[0];
$desiredSuper = strtoupper($functionName);
if(in_array($desiredSuper, self::$supers)){
doStuff ( $_{$desiredSuper}[$index] );
}
else{
throw new Exception("$desiredSupper is not an allowed superGlobal");
}
}
}
you could then do:
example::get('id'); //wo do stuff to $_GET['id']
example::server('REQUEST_METHOD'); //Will do stuff to $_SERVER['REQUEST_METHOD']
example::foo('bar'); //throws Exception: 'FOO is not an allowed superGlobal'
Php manual on magic methods: http://ca.php.net/manual/en/language.oop5.overloading.php#language.oop5.overloading.methods
Edit
I just noticed your edit, you could try:
$X = {$X};
You can use $_REQUEST["var"] instead of $_GET["var"] or $_POST["var"].
A more complicated way would be to test if the variable exists in the GET array, if it doesnt then its POST. If it does its GET.
$var = null;
if (isset($_GET["varname"]))
{
$var = $_GET["varname"];
}
else
{
$var = $_POST["varname"];
}
If you want a variable to be accessible globally, you can add it tot he $GLOBALS array.
$GLOBALS['test']='test';
Now you can fetch $GLOBALS['test'] anywhere.