bears

$xml = '<response>
<systime0>2324</systime0>
<iovalue0>1000000000000000000001</iovalue0>
<pwm0>0</pwm0>
<adc0>635</adc0>
<adc1>561</adc1>
<adc2>527</adc2>
<adc3>652</adc3>
<count0>0</count0>
<count1>0</count1>
<count2>0</count2>
<count3>0</count3>
<slow_info0/>
<cat_inf0/>
<cat_cnt0/>
</response>';

$data = new SimpleXMLElement($xml);
$data = str_split($data->iovalue0);
$data = implode('|', $data);

var_dump($data);

// Результат
string '1|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|1' (length=43)