I'm trying to determine whether or not there is a value passed, but the value CAN be 0 ...
isset always returns true, and empty returns false because the value is 0
How can I get around this?
try
bool array_key_exists ( mixed $key , array $array )
like
if (array_key_exists("var1", $_POST)) {
// positive case, var1 was posted
if ($_POST["var1"] == 0){
// var1 was posted and 0
}else{
// var1 was posted and is not 0
}
}
more details are given at the docs.
The values of the $_POST array is all strings. Use the === operator:
if ($_POST['key'] === '0') {
// do things
}
Try this
if (isset($_POST['name']) && $_POST['name'] != 0)) {
/your Code/
}
What about simply checking whether the value is empty:
if (isset($_POST['key']) && $_POST['key'] !== '')) {
//'key' is set and not empty
}
All post values are strings, so consider:
isset($a[i]) && strlen($a[i])
Which will be true if and only if a value (except "an empty string") is supplied. Unlike with empty, which would return FALSE, this will also detect when "0" was passed as a value. Unlike the proposed solution, it will not be true when "" was supplied: thus it truly detects when a value was passed.
Also, array_key_exists and isset for $_POST keys will work the same, as there will no NULL values; arguably the critical check is that for a non-empty string. Once a value has been determined to exist (per the above/desired rules), it can be processed as appropriate - e.g. if ($a[i] > 0) or if ($a[i] == 0).
Possibly a strange one that I hope can be done in one line.
I have to have an IF statement that will checks two things.
The first checks if the variable $loggedInfo['status'] is set and is equal to "client".
The second checks that the variable $loggedInfo['address1'] is set and is blank.
The reason being that when the first variable equals staff then the 'address1' variable doesn't exist.
I did have the following but when I log in as staff it still checks for the address1
if((isset($loggedInfo['status'])=="client")&&(!$loggedInfo['address1'])){
//Do something
}
isset returs true or false. you have to do separate check for the actual value
if(
isset($loggedInfo['status']) && $loggedInfo['status']=="client" &&
isset($loggedInfo['address1']) && trim($loggedInfo['address1']) != ''
)
{
//Do something
}
if((isset($loggedInfo['status']) && $loggedInfo['status']=="client") &&(empty($loggedInfo['address1'])){
//Do something
}
isset() returns TRUE if the given variable is defined in the current scope with a non-null value.
empty() returns TRUE if the given variable is not defined in the current scope, or if it is defined with a value that is considered "empty". These values are:
NULL // NULL value
0 // Integer/float zero
'' // Empty string
'0' // String '0'
FALSE // Boolean FALSE
array() // empty array
Depending PHP version, an object with no properties may also be considered empty.
Well you just can't compare the return value of isset() with the string "client", because it will never equal that. To quote http://php.net/manual/en/function.isset.php its return values are "TRUE if var exists and has value other than NULL, FALSE otherwise".
First check if it is set
if ((isset($loggedInfo['status']) === true) && ($loggedInfo['status'] === "client") && (empty($loggedInfo['address1']) === true)) {
// Do something
}
Key take away from this should be to look up return values for every function you use, like empty(), in the manual http://www.php.net/manual/en/function.empty.php. This will save you a lot of headaches in the future.
I want to check if the app parameter exists in the URL, but has no value.
Example:
my_url.php?app
I tried isset() and empty(), but don’t work. I’ve seen it done before and I forgot how.
Empty is correct. You want to use both is set and empty together
if(isset($_GET['app']) && !empty($_GET['app'])){
echo "App = ".$_GET['app'];
} else {
echo "App is empty";
}
empty should be working (if(empty($_GET[var]))...) as it checks the following:
The following things are considered to be empty:
"" (an empty string)
0 (0 as an integer)
0.0 (0 as a float)
"0" (0 as a string)
NULL
FALSE
array() (an empty array)
$var; (a variable declared, but without a value)
Here are your alternatives:
is_null - Finds whether a variable is NULL
if(is_null($_GET[var])) ...
defined - Checks whether a given named constant exists
if(defined($_GET[var])) ...
if( isset($_GET['app']) && $_GET['app'] == "")
{
}
You can simply check that by array_key_exists('param', $_GET);.
Imagine this is your URL: http://example.com/file.php?param. It has the param query parameter, but it has not value. So its value would be null actually.
array_key_exists('param', $_GET); returns true if param exists; returns false if it doesn't exist at all.
Which is better to use when I use _GET['something here'] for a variable to check if it is empty or not
if (isset($_GET['url']) != '') {
//do stuff with it
}
OR
if (isset($_GET['url']) != NULL) {
//do stuff with it
}
'' or null or something else?
Please don't call this over optimizing or micro optimizing, I am simply looking for best practices, thank you
Use empty() - it actually first test of the variable exists before testing whether something is in it.
[Edit: isset() returns only TRUE or FALSE, so both of the statements above work equally well]
You should do the following to be sure that the value both exists and isn't empty
if(isset($_POST[myField]) && $_POST[myField] != "") {
Do my PHP code
}
PHP can be a little painful when debugging blank/missing/empty value checks. You can use empty() or isset(), but remember the cases where empty returns true. It's highly liberal with what it considers empty.
Returns FALSE if var has a non-empty and non-zero value.
The following things are considered to be empty:
"" (an empty string)
0 (0 as an integer)
"0" (0 as a string)
NULL
FALSE
array() (an empty array)
var $var; (a variable declared, but without a value in a class)
isset is more conservative in that it only checks for variable's existence and a NULL value. From the documentation:
Returns TRUE if var exists and has value other than NULL, FALSE otherwise.
I read somewhere that the isset() function treats an empty string as TRUE, therefore isset() is not an effective way to validate text inputs and text boxes from a HTML form.
So you can use empty() to check that a user typed something.
Is it true that the isset() function treats an empty string as TRUE?
Then in which situations should I use isset()? Should I always use !empty() to check if there is something?
For example instead of
if(isset($_GET['gender']))...
Using this
if(!empty($_GET['gender']))...
isset vs. !empty
FTA:
"isset() checks if a variable has a
value including (False, 0 or empty
string), but not NULL. Returns TRUE
if var exists; FALSE otherwise.
On the other hand the empty() function
checks if the variable has an empty
value empty string, 0, NULL or
False. Returns FALSE if var has a
non-empty and non-zero value."
In the most general way :
isset tests if a variable (or an element of an array, or a property of an object) exists (and is not null)
empty tests if a variable (...) contains some non-empty data.
To answer question 1 :
$str = '';
var_dump(isset($str));
gives
boolean true
Because the variable $str exists.
And question 2 :
You should use isset to determine whether a variable exists ; for instance, if you are getting some data as an array, you might need to check if a key isset in that array.
Think about $_GET / $_POST, for instance.
Now, to work on its value, when you know there is such a value : that is the job of empty.
Neither is a good way to check for valid input.
isset() is not sufficient because – as has been noted already – it considers an empty string to be a valid value.
! empty() is not sufficient either because it rejects '0', which could be a valid value.
Using isset() combined with an equality check against an empty string is the bare minimum that you need to verify that an incoming parameter has a value without creating false negatives:
if( isset($_GET['gender']) and ($_GET['gender'] != '') )
{
...
}
But by "bare minimum", I mean exactly that. All the above code does is determine whether there is some value for $_GET['gender']. It does not determine whether the value for $_GET['gender'] is valid (e.g., one of ("Male", "Female","FileNotFound")).
For that, see Josh Davis's answer.
isset is intended to be used only for variables and not just values, so isset("foobar") will raise an error. As of PHP 5.5, empty supports both variables and expressions.
So your first question should rather be if isset returns true for a variable that holds an empty string. And the answer is:
$var = "";
var_dump(isset($var));
The type comparison tables in PHP’s manual is quite handy for such questions.
isset basically checks if a variable has any value other than null since non-existing variables have always the value null. empty is kind of the counter part to isset but does also treat the integer value 0 and the string value "0" as empty. (Again, take a look at the type comparison tables.)
If you have a $_POST['param'] and assume it's string type then
isset($_POST['param']) && $_POST['param'] != '' && $_POST['param'] != '0'
is identical to
!empty($_POST['param'])
isset() is not an effective way to validate text inputs and text boxes from a HTML form
You can rewrite that as "isset() is not a way to validate input." To validate input, use PHP's filter extension. filter_has_var() will tell you whether the variable exists while filter_input() will actually filter and/or sanitize the input.
Note that you don't have to use filter_has_var() prior to filter_input() and if you ask for a variable that is not set, filter_input() will simply return null.
When and how to use:
isset()
True for 0, 1, empty string, a string containing a value, true, false
False for null
e.g
$status = 0
if (isset($status)) // True
$status = null
if (isset($status)) // False
Empty
False for 1, a string containing a value, true
True for null, empty string, 0, false
e.g
$status = 0
if(empty($status)) // true
$status = 1
if(empty($status)) // False
isset() vs empty() vs is_null()
isset is used to determine if an instance of something exists that is, if a variable has been instantiated... it is not concerned with the value of the parameter...
Pascal MARTIN... +1
...
empty() does not generate a warning if the variable does not exist... therefore, isset() is preferred when testing for the existence of a variable when you intend to modify it...
isset() is used to check if the variable is set with the value or not and Empty() is used to check if a given variable is empty or not.
isset() returns true when the variable is not null whereas Empty() returns true if the variable is an empty string.
isset($variable) === (#$variable !== null)
empty($variable) === (#$variable == false)
I came here looking for a quick way to check if a variable has any content in it. None of the answers here provided a full solution, so here it is:
It's enough to check if the input is '' or null, because:
Request URL .../test.php?var= results in $_GET['var'] = ''
Request URL .../test.php results in $_GET['var'] = null
isset() returns false only when the variable exists and is not set to null, so if you use it you'll get true for empty strings ('').
empty() considers both null and '' empty, but it also considers '0' empty, which is a problem in some use cases.
If you want to treat '0' as empty, then use empty(). Otherwise use the following check:
$var .'' !== '' evaluates to false only for the following inputs:
''
null
false
I use the following check to also filter out strings with only spaces and line breaks:
function hasContent($var){
return trim($var .'') !== '';
}
Using empty is enough:
if(!empty($variable)){
// Do stuff
}
Additionally, if you want an integer value it might also be worth checking that intval($variable) !== FALSE.
I use the following to avoid notices, this checks if the var it's declarated on GET or POST and with the # prefix you can safely check if is not empty and avoid the notice if the var is not set:
if( isset($_GET['var']) && #$_GET['var']!='' ){
//Is not empty, do something
}
$var = '';
// Evaluates to true because $var is empty
if ( empty($var) ) {
echo '$var is either 0, empty, or not set at all';
}
// Evaluates as true because $var is set
if ( isset($var) ) {
echo '$var is set even though it is empty';
}
Source: Php.net
isset() tests if a variable is set and not null:
http://us.php.net/manual/en/function.isset.php
empty() can return true when the variable is set to certain values:
http://us.php.net/manual/en/function.empty.php
<?php
$the_var = 0;
if (isset($the_var)) {
echo "set";
} else {
echo "not set";
}
echo "\n";
if (empty($the_var)) {
echo "empty";
} else {
echo "not empty";
}
?>
!empty will do the trick. if you need only to check data exists or not then use isset other empty can handle other validations
<?php
$array = [ "name_new" => "print me"];
if (!empty($array['name'])){
echo $array['name'];
}
//output : {nothing}
////////////////////////////////////////////////////////////////////
$array2 = [ "name" => NULL];
if (!empty($array2['name'])){
echo $array2['name'];
}
//output : {nothing}
////////////////////////////////////////////////////////////////////
$array3 = [ "name" => ""];
if (!empty($array3['name'])){
echo $array3['name'];
}
//output : {nothing}
////////////////////////////////////////////////////////////////////
$array4 = [1,2];
if (!empty($array4['name'])){
echo $array4['name'];
}
//output : {nothing}
////////////////////////////////////////////////////////////////////
$array5 = [];
if (!empty($array5['name'])){
echo $array5['name'];
}
//output : {nothing}
?>
Please consider behavior may change on different PHP versions
From documentation
isset() Returns TRUE if var exists and has any value other than NULL. FALSE otherwise
https://www.php.net/manual/en/function.isset.php
empty() does not exist or if its value equals FALSE
https://www.php.net/manual/en/function.empty.php
(empty($x) == (!isset($x) || !$x)) // returns true;
(!empty($x) == (isset($x) && $x)) // returns true;
When in doubt, use this one to check your Value and to clear your head on the difference between isset and empty.
if(empty($yourVal)) {
echo "YES empty - $yourVal"; // no result
}
if(!empty($yourVal)) {
echo "<P>NOT !empty- $yourVal"; // result
}
if(isset($yourVal)) {
echo "<P>YES isset - $yourVal"; // found yourVal, but result can still be none - yourVal is set without value
}
if(!isset($yourVal)) {
echo "<P>NO !isset - $yourVal"; // $yourVal is not set, therefore no result
}