What's quicker and better to determine if an array key exists in PHP?

isset() is faster, but it's not the same as array_key_exists().

array_key_exists() purely checks if the key exists, even if the value is NULL.

Whereas isset() will return false if the key exist and value is NULL.

If you are interested in some tests I've done recently:

https://stackoverflow.com/a/21759158/520857

Summary:

| Method Name                              | Run time             | Difference
=========================================================================================
| NonExistant::noCheckingTest()            | 0.86004090309143     | +18491.315775911%
| NonExistant::emptyTest()                 | 0.0046701431274414   | +0.95346080503016%
| NonExistant::isnullTest()                | 0.88424181938171     | +19014.461681183%
| NonExistant::issetTest()                 | 0.0046260356903076   | Fastest
| NonExistant::arrayKeyExistsTest()        | 1.9001779556274      | +209.73055713%

Well, the main difference is that isset() will not return true for array keys that correspond to a null value, while array_key_exists() does.

Running a small benchmark shows that isset() it's faster but it may not be entirely accurate.