Find a high multiplicative persistence in PHP

search.php

<?php

// INPUT VARS
$start  = 2677889;
$end    = 26888999;

/**
 * @param integer $input
 * @return false|int
 */
function search($input)
{
    $str = (string)$input;
    $loop = $str[0];
    $strlen = strlen($str);
    for ($i = 1; $i < $strlen; $i++) {
        // Check for:
        // - Non-increasing digits left to right
        // - Zero's
        // - Adjacent digits less than 10 when multiplied (*24*579 is simplified to 57*8*9)
        if ($str[$i] < $loop || $str[$i] === '0' || ($i + 1 < $strlen && $str[$i] * $str[$i + 1] <= 10)) {
            return false;
        }
        $loop = $str[$i];
    }

    return check($str);
}

/**
 * @param string $str
 * @param int $step
 * @return int
 */
function check($str, $step = 0)
{
    $total = 1;
    for ($i = 0; $i < strlen($str); $i++) {
        $total *= $str[$i];
    }
    $step++;
    if (strlen($total) === 1) {
        return $step;
    }

    return check((string)$total, $step);
}

$results = [];

for ($i = $start; $i <= $end; $i++) {
    $result = search($i);
    if (!$result) {
        continue;
    }
    if (!array_key_exists($result, $results)) {
        $results[$result] = $i;
    } else {
        if ($results[$result] > $i) {
            $results[$result] = $i;
        }
    }
}

foreach ($results as $count => $number) {
    echo $count . ' => ' . $number . '<br />';
}