What's the difference between isset() and array_key_exists()?
96246
What's quicker and better to determine if an array key exists in PHP?
17184
Are arrays in PHP copied as value or as reference to new variables, and when passed to functions?
156640
How can I check if a string exists in another string
4521
Is there an "exists" function for jQuery?
69750
MySQL check if a table exists without throwing an exception
40229
How do I check if a variable exists?
76864
What is the best way to check if a URL exists in PHP?
70566
How do I check if an object has a key in JavaScript?
49486
Problem with $_POST, if isset() and mysql_fetch_assoc(): echo returns correct value, page source always returns else value
123446
How to loop through an associative array and get the key?
24725
isset() function is returning true even when item is not set
26815
In PHP, how do you change the key of an array element?
14424
What is the difference between session_unset() and session_destroy() in PHP?
145656
Weak typing in PHP: why use isset at all?
135172
Fully Understanding PDO ATTR_PERSISTENT
85438
In PHP, what is a closure and why does it use the "use" identifier?
110913
Difference in accessing arrays in PHP 5.3 and 5.4 or some configuration mismatch?