IIRC, you can use get_defined_vars() for this: $foo = NULL; $vars = get_defined_vars(); if (array_key_exists(‘bar’, $vars)) {}; // Should evaluate to FALSE if (array_key_exists(‘foo’, $vars)) {}; // Should evaluate to TRUE
Update for PHP 7 (thanks shock_gone_wild) PHP 7 introduces the null coalescing operator which simplifies the below statements to: $var = $var ?? “default”; Before PHP 7 No, there is no special operator or special syntax for this. However, you could use the ternary operator: $var = isset($var) ? $var : “default”; Or like this: … Read more
Most form inputs are always set, even if not filled up, so you must check for the emptiness too. Since !empty() is already checks for both, you can use this: if (!empty($_POST[“mail”])) { echo “Yes, mail is set”; } else { echo “No, mail is not set”; }
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 … Read more
If the variable you are checking would be in the global scope you could do: array_key_exists(‘v’, $GLOBALS)
I generally use the typeof operator: if (typeof obj.foo !== ‘undefined’) { // your code here } It will return “undefined” either if the property doesn’t exist or its value is undefined. (See also: Difference between undefined and not being defined.) There are other ways to figure out if a property exists on an object, … Read more