Question

Getting an Undefined Offset error here — apparently from the $newval array.

Note that the {exp} tag is not PHP, and is simply a sql query by my CMS system which creates the $bags array for me.

<?php

$bags = array();
$newval = array();
$pattern = "[^0-9]";

{exp:query sql="SELECT m_field_id_1 as bags FROM exp_member_data WHERE m_field_id_1 IS NOT NULL"}
$bags[] = "{bags}";
{/exp:query}

foreach ($bags as $key => $value) {
for ( $i = 0, $s = strlen($value); $i < $s; $i++) {
    if ( is_numeric($value[$i]) ) {
        $newval[$key] .= $value[$i];
    }
}
}

$sum = array_sum($newval);
$format = number_format($sum);

echo $format;

?>

Answer 1

Before you can concatenate to a variable, that variable must exist (to avoid a Notice). Simply declare $newval[$key] as an empty string before the for loop:

foreach ($bags as $key => $value) {
    $newval[$key] = '';
    for ($i = 0, $s = strlen($value); $i < $s; $i++) {
        if ( is_numeric($value[$i]) ) {
            $newval[$key] .= $value[$i];
        }
    }
}

By the way, there’s nothing wrong with your starting value of $i. It is correct to have it at 0 and not 1 as others are suggesting.

However, if you’re trying to remove non-number characters from a string and avoid empty array elements (as your original code does), you can remove the inner for loop and simply:

foreach ($bags as $key => $value) {
    $digits = preg_replace('/[^0-9]/', '', $value);
    if (strlen($digits)) {
        $newval[$key] = $digits;
    }
}