Here is the quick article which shows the difference between two PHP functions which are [code]isset()[/code] and [code]array_key_exists()[/code].
One basic difference is that isset() can be used with array and variables both while array_key_exists() can be used with the arrays only.
But the major difference lies in the values they return on certain condition. Main difference comes into picture while you are dealing with the [code]NULL[/code] values.
So now lets check the major difference now.
Both this function return [code]TRUE[/code] on success and [code]FALSE[/code] on error. Here success means variable is available and error means variable is not available.
array_key_exists()
array_key_exists() will check for the existence of the key only. This function will return true even if that array element contain the [code]NULL[/code]. Have a look at below code block for the same.
[cc lang=”php”]
$arr = array(
“one”=>”1”,
“two”=>”2”,
“three”=>null
);
array_key_exists(“one”, $arr); // true
array_key_exists(“two”, $arr); // true
array_key_exists(“three”, $arr); // true
[/cc]
isset()
Unlike array_key_exists(), isset() will check the existence plus the value of the varible. This function will return true only if variable is exists and contain non null value. So this function will return false even if variable is exists but contain the NULL value.
Have a look at below code block for the same:
[cc lang=”php”]
$arr = array(
“one”=>”1”,
“two”=>”2”,
“three”=>null
);
isset($arr[“one”]); // true
isset($arr[“two”]); // true
isset($arr[“three”]); // false
[/cc]
Conclusion
Here is the difference between these two functions, now be careful while using any of the function mentioned above.
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Hi,
Thank you for this information. :)
Isset-Example:
Second “two” has to be “three” :D
I think there should be ‘three’ => null in isset() code part.
Hi Avinash,
I think the third array element in the isset() example and the third isset() call has to be “three” not “two”? Otherwise it doesn’t make sense I think…
Michael
Did you put this on purpose?
[cc lang=”php”]
$arr = array(
“one”=>”1”,
“two”=>”2”,
“two”=>null
);
isset($arr[“one”]); // true
isset($arr[“two”]); // true
isset($arr[“two”]); // false
[/cc]
I think you probably meant:
[cc lang=”php”]
$arr = array(
“one”=>”1”,
“two”=>”2”,
“three”=>null
);
isset($arr[“one”]); // true
isset($arr[“two”]); // true
isset($arr[“three”]); // false
[/cc]
The second example should probably use:
[cc lang=”php”]
$arr = array(
“one”=>”1”,
“two”=>”2”,
“three”=>null
);
[/cc]
However, there is one more difference between the two. array_key_exists requires second argument to be declared and to be an array. This code has serious issues but it silently returns true:
[cc lang=”php”]
$string = “”;
isset ( $string[“key”] ); // false
isset ( $noSuchVar[“key”] ); // false
[/cc]
There is really very few reasons to use isset in well written code.
thanks to you all for notifying the mistake in code , corrected now :)
I don’t think you are evaluation these two on the right basis. The array_key_exists(“three”, $arr) will always return true because the KEY exists. isset($arr[‘three’]) however is checking the value stored in the “three” index of $arr which will return false because the VALUE is null.
I think you are comparing apples to pears here mate.
My main concern for this article is for isset() function, because most of the developer thinks this function is used to check the existence of the variable but its not like that. It will check the existence plus value of that variable also. while array_key_exists() will not check for the value of the variable anyhow.
That’s fair enough. I didn’t get that from the post.