- explode: documentation ( source)
<?php
$search = '35';
$range = '';
$arr = [
'0' => '0;0',
'1' => '20;0-20',
'2' => '50;20-50',
'3' => '100;50-100',
'4' => '200;100-200',
'5' => '500;200-500'
];
foreach ( $arr as $k => $v ) {
$values = explode(";", $v);
$key = $values[0];
$range = $values[1];
if ( $key >= $search ) break;
} echo $key;