Question

How to handle undefined array key in PHP

Answer 1

// Use isset() to determine if array key is null or not
 
 
$arr = array();
 
if (isset($arr[0])) {
    $arr[0]++;
} else {
    $arr[0] = 1;
}
 
var_dump($arr);
 
 
 
 
 
 
/*
run:
 
array(1) {
  [0]=>
  int(1)
}
 
*/

 

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Answer 2

// Use isset() to determine if array key is null or not

$arr = array();

for ($i = 0; $i < 3; $i++) {
    if (isset($arr[0])) {
        $arr[0]++;
    } else {
        $arr[0] = 1;
    }
}

var_dump($arr);






/*
run:

array(1) {
  [0]=>
  int(3)
}

*/

 

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