Array skips the numeric index when adding element? - php

Question

I've faced funny bug when modifying the e-store engine:
// ...
$this->toolbar_title[] = 'Products';
// ...
print_r($this->toolbar_title);
/*
Array (
[0] => Products
)
*/
$this->toolbar_title[] = 'Filtered by: name';
print_r($this->toolbar_title);
/*
Array
(
[0] => Products
[2] => Filtered by: name
)
*/
// ...
wat??? where is the "1" index??
Tried to reproduce this in clean stand-alone php script - nope! the added element has index "1" as expected. but when doing the same within the engine code - new element has index "2".
There are no setters, no "[]" overloading found, even no any access to the $this->toolbar_title elements by index, only pushing via [];
What the magic is this? What and where should I seek to find the reason?
PHP 5.6, PrestaShop 1.6 engine.
Thanks a lot in advance for any clue.
UPD: the exact code fragment from engine
if ($filter = $this->addFiltersToBreadcrumbs()) {
echo'131-';print_r($this->toolbar_title);
$this->toolbar_title[] = $filter;
echo'132-';var_dump($this->toolbar_title);
}
where addFiltersToBreadcrumbs returns the string and make NO any access to toolbar_title
UPD2:
public function addFiltersToBreadcrumbs()
{
if ($this->filter && is_array($this->fields_list)) {
$filters = array();
foreach ($this->fields_list as $field => $t) {
if (isset($t['filter_key'])) {
$field = $t['filter_key'];
}
if (($val = Tools::getValue($this->table.'Filter_'.$field)) || $val = $this->context->cookie->{$this->getCookieFilterPrefix().$this->table.'Filter_'.$field}) {
if (!is_array($val)) {
$filter_value = '';
if (isset($t['type']) && $t['type'] == 'bool') {
$filter_value = ((bool)$val) ? $this->l('yes') : $this->l('no');
} elseif (isset($t['type']) && $t['type'] == 'date' || isset($t['type']) && $t['type'] == 'datetime') {
$date = Tools::unSerialize($val);
if (isset($date[0])) {
$filter_value = $date[0];
if (isset($date[1]) && !empty($date[1])) {
$filter_value .= ' - '.$date[1];
}
}
} elseif (is_string($val)) {
$filter_value = htmlspecialchars($val, ENT_QUOTES, 'UTF-8');
}
if (!empty($filter_value)) {
$filters[] = sprintf($this->l('%s: %s'), $t['title'], $filter_value);
}
} else {
$filter_value = '';
foreach ($val as $v) {
if (is_string($v) && !empty($v)) {
$filter_value .= ' - '.htmlspecialchars($v, ENT_QUOTES, 'UTF-8');
}
}
$filter_value = ltrim($filter_value, ' -');
if (!empty($filter_value)) {
$filters[] = sprintf($this->l('%s: %s'), $t['title'], $filter_value);
}
}
}
}
if (count($filters)) {
return sprintf($this->l('filter by %s'), implode(', ', $filters));
}
}
}

Answer 1

For php, if you unset one index in array, the index will appear discontinuous growth.
$this->toolbar_title = array_values($this->toolbar_title);
will rebuild the index.