undefined variable php code example

Example 1: undefined variable inside function php

$myId = 0;
function run(){
  global $myId;
	echo $myId;
}

Example 2: php undefined index

// Your array index has no value or is not referencing anything,
// The easiest way to overcome this is to simply check whether
// it has been defined
if (isset($arr[$i])) {
	// Do something
}

Example 3: php Undefined

if (isset($variable)) { /* do something */ };