Undefined Offset PHP error, arrays are defined - php

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;
}
}

Answer 2

As Jrod said you're walking through the characters in $value but you start at 0. strlen() returns the absolute amount of chars in $value so in your for loop you should start at 1 instead of 0.
This is the code you should use:
<?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) {
$newval[$key] = '';
for ( $i = 1, $s = strlen($value); $i < $s; $i++) {
if ( is_numeric($value[$i]) ) {
$newval[$key] .= $value[$i];
}
}
}
$sum = array_sum($newval);
$format = number_format($sum);
echo $format;
?>

Answer 3

Instead of this
foreach ($bags as $key => $value) {
for ( $i = 0, $s = strlen($value); $i < $s; $i++) {
if ( is_numeric($value[$i]) ) {
$newval[$key] .= $value[$i];
}
}
}
you can write
$newval = preg_replace('~\D+~', '', $bags);
one line is easier to debug than six, isn't it.