Online PHP editor | output for v1VOD

<?php function gdr_encode($val) { // all characters that json encode without escaping $chrs = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789 !#$%&\'()*+,-.:;<=>?@[]^_`{|}~'; $base = strlen($chrs); $str = ''; while ($val > 0) { $str = $chrs[$val % $base] . $str; $val = (int)($val / $base); } return $str; } function gdr_decode($str) { // all characters that json encode without escaping $chrs = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789 !#$%&\'()*+,-.:;<=>?@[]^_`{|}~'; $base = strlen($chrs); $map = array(); for ($i=0; $i<$base; $i++) { $map[$chrs[$i]] = $i; } $val = 0; for ($i=0; $i<strlen($str); $i++) { $val *= $base; $val += (int)$map[$str[$i]]; } return $val; } function duration($val) { if ($val < 24) { return sprintf('%d', $val).'h'; } if ($val < 24*10) { return sprintf('%1.1f', $val/24).'d'; } if ($val < 168*10) { return sprintf('%1.1f', $val/168).'w'; } //if ($val < 730*10) { // return sprintf('%1.1f', $val/730).'m'; //} return sprintf('%1.1f', $val/8760).'y'; } function cmp($val) { return strlen(gdr_encode($val))+2-strlen($val); } function insert(&$vals, $n) { $min = intval('1'.str_repeat('0', $n-1)); $max = intval(str_repeat('9', $n)); $vals[] = $min; $vals[] = $max; $cmp = cmp($min); $cmp_max = cmp($max); if ($cmp === $cmp_max) { return; } while ($min < $max) { $mid = (int)($min+$max)/2); $k = cmp($mid); echo "$min=>$cmp $mid=>$k $max=>$cmp_max\n"; if ($k == $cmp && $k !== cmp($mid+1)) { $vals[] = $mid; $vals[] = $mid+1; return; } if ($k > $cmp) { $max = $mid-1; } else { $min = $mid+1; } } } $vals = array(0); for ($i=1; $i<8; $i++) { insert($vals, $i); } $vals = array_unique($vals); sort($vals); //$vals = array( // 0, 1, 99, 100, 255, 256, 999, 1000, 9999, 10000, 65535, 65536, 99999, // 100000, 250000, 500000, 750000, 999999, 1000000, 9999999, //4294967295, 4294967296 //); echo sprintf("%7s %7s %7s %4s\n", 'num', 'str', 'time', 'cmp'); foreach ($vals as $val) { $enc = gdr_encode($val); $dec = gdr_decode($enc); if ($dec !== $val) { echo "ERROR: $val => $enc => $dec\n"; } else { echo sprintf("%7d %7s %7s %4d\n", $dec, "\"$enc\"", duration($val), strlen($enc)+2-strlen($val)); } }