Project Euler Problem 8

Project Euler Problem 8: Discover the largest product of five consecutive digits in the 1000-digit number.

<?php

$n = "73167176531330624919225119674426574742355349194934"
    ."96983520312774506326239578318016984801869478851843"
    ."85861560789112949495459501737958331952853208805511"
    ."12540698747158523863050715693290963295227443043557"
    ."66896648950445244523161731856403098711121722383113"
    ."62229893423380308135336276614282806444486645238749"
    ."30358907296290491560440772390713810515859307960866"
    ."70172427121883998797908792274921901699720888093776"
    ."65727333001053367881220235421809751254540594752243"
    ."52584907711670556013604839586446706324415722155397"
    ."53697817977846174064955149290862569321978468622482"
    ."83972241375657056057490261407972968652414535100474"
    ."82166370484403199890008895243450658541227588666881"
    ."16427171479924442928230863465674813919123162824586"
    ."17866458359124566529476545682848912883142607690042"
    ."24219022671055626321111109370544217506941658960408"
    ."07198403850962455444362981230987879927244284909188"
    ."84580156166097919133875499200524063689912560717606"
    ."05886116467109405077541002256983155200055935729725"
    ."71636269561882670428252483600823257530420752963450";

for ($i = $p = 0, $q = 1; $i < strlen($n)-4; $i++, $q = 1)
  for ($j = 0; $j < 5; $j++)
    $p = max($p, ($q *= $n[$i+$j]));
echo $p;

?>