PHP While loop Notice: Undefined offset

Question

I am fixing an existing PHP code

I get error

Notice: Undefined offset: 6

The PHP code will look like below. It is a big while loop. Here I just show the main section.

$data = Array
(
    [0] => 1
)

$data2 = Array
(
    [0] => 1
    [1] => 10
    [2] => 12
    [3] => 15
    [4] => 17
    [5] => 23
)


$i = 0;
while($data[$i]){
    array_push($data,$data2);
    $i++;
}

Also,

Sometimes, I get error

Notice: Undefined offset: 4

for

$data2 = Array
(
    [0] => 12
    [1] => 34
    [2] => 56
    [3] => 78
    [4] => 83
)

How do I fix this issue?

Try a foreach loop instead : php.net/manual/en/control-structures.foreach.php — CD001
– CD001, Commented Jun 12, 2015 at 13:42
while( isset($data[$i]) ) { The condition needs to be boolean TRUE or FALSE. Though you'd be best to use a foreach loop to traverse through an array. — ʰᵈˑ
– ʰᵈˑ, Commented Jun 12, 2015 at 13:46
What???? I don't understand what you are doing here... you are adding the whole array $data2 to the end of $data while there is a value in $data that sounds non-sense to me...? — n00dl3
– n00dl3, Commented Jun 12, 2015 at 13:47
@JuniusRendel I know this code is confusing. I am still trying to figure out what was in developer's mind when he wrote this code. — Peter
– Peter, Commented Jun 12, 2015 at 13:55

Richard · Accepted Answer · 2015-06-12 13:45:40Z

7

You should use foreach for iterating through arrays:

foreach($data as $key => $value) {}

Your warning with while is that you do check if this array position exists right. Use this instead:

while(isset($data[$i])){}

answered Jun 12, 2015 at 13:45

Richard

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2 Comments

ʰᵈˑ Over a year ago

Note: Using isset in the while condition because the condition needs to equate to boolean TRUE/FALSE; which isset will do (also handling the undefined offset).

Peter Over a year ago

Thanks Richard Reiber and @ʰᵈˑ

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