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 asTRUE
?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']]]...
rath3r
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asked Aug 2, 2009 at 19:00
1
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."
simhumileco
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answered Aug 2, 2009 at 19:04
dassoukidassouki
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3
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
/ $_POST
, for instance.
Now, to work on its value, when you know there is such a
value : that is the job of empty
.
answered Aug 2, 2009 at 19:06
Pascal MARTINPascal MARTIN
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Neither is a good way to check for valid input.
isset[]
is not sufficient because – as has been noted already – it considers an empty string to be a valid value.! empty[]
is not sufficient either because it rejects '0', which could be a valid value.
Using isset[]
combined with an equality check against an empty string is the bare minimum that you need to verify
that an incoming parameter has a value without creating false negatives:
if[ isset[$_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.
answered Apr 22, 2012 at 4:24
1
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.]
answered Aug 2, 2009 at 19:12
GumboGumbo
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1
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']]
answered Jan 26, 2013 at 17:18
macio.Junmacio.Jun
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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
.
answered Aug 2, 2009 at 20:59
Josh DavisJosh Davis
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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
answered May 14, 2017 at 7:18
Fokwa BestFokwa Best
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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...
answered Jun 13, 2014 at 12:04
MikeMike
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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.
answered May 17, 2018 at 15:23
isset[] vs empty[] vs is_null[]
answered Nov 28, 2019 at 20:33
Foued MOUSSIFoued MOUSSI
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isset[$variable] === [@$variable !== null]
empty[$variable] === [@$variable == false]
answered Aug 2, 2009 at 19:06
moomoo
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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[$var .''] !== '';
}
answered Feb 25, 2020 at 20:48
potatopotato
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Using empty
is enough:
if[!empty[$variable]]{
// Do stuff
}
Additionally, if you want an integer value it might also be worth checking that intval[$variable] !== FALSE
.
answered Aug 2, 2009 at 19:05
YouYou
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2
I use the following to avoid notices, this checks if the var it's declarated on GET or POST and with the @ prefix you can safely check if is not empty and avoid the notice if the var is not set:
if[ isset[$_GET['var']] && @$_GET['var']!='' ]{
//Is not empty, do something
}
answered Aug 7, 2017 at 18:08
AztrozeroAztrozero
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2
$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 '$var is set even though it is empty';
}
Source: Php.net
answered Jul 10, 2018 at 11:40
csandreas1csandreas1
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!empty will do the trick. if you need only to check data exists or not then use isset other empty can handle other validations
answered Jun 3, 2020 at 9:34
When in doubt, use this one to check your Value
and to clear your head on the
difference between isset
and empty
.
if[empty[$yourVal]] {
echo "YES empty - $yourVal"; // no result
}
if[!empty[$yourVal]] {
echo "NOT !empty- $yourVal"; // result
}
if[isset[$yourVal]] {
echo "
YES isset - $yourVal"; // found yourVal, but result can still be none - yourVal is set without value
}
if[!isset[$yourVal]] {
echo "
NO !isset - $yourVal"; // $yourVal is not set, therefore no result
}
answered Oct 16, 2021 at 0:05
KJSKJS
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What can I use instead of isset in PHP?
The equivalent of isset[$var] for a function return value is func[] === null . isset basically does a !== null comparison, without throwing an error if the tested variable does not exist.
Should I use isset?
isset[] is best for radios/checkboxes. Use empty[] for strings/integer inputs. when a variable contains a value, using isset[] will always be true. you set the variable yourself, so it's not a problem.
Does Isset check for empty string?
"isset[] checks if a variable has a value including [False, 0 or empty string], but not NULL.
What's the difference between isset [] and Array_key_exists []?
Difference between isset[] and array_key_exists[] Function: The main difference between isset[] and array_key_exists[] function is that the array_key_exists[] function will definitely tells if a key exists in an array, whereas isset[] will only return true if the key/variable exists and is not null.