php array_search返回非匹配元素

Question

When I try to find collision in a hash value using php, there is a problem. I can find the first 3 byte collision successfully. However when I try to find the 10 byte collision the array_search does not work. It return some non match value to me. Can anyone help me? Here is my code.

<?php 
$array = array();
$do = true;
do {
  $num1= rand(1,90000);
  $num2= rand(1,90000);

  $testcase2 = $num1."14040371D".$num2;
  $testcase1 = (string)$testcase2;
  $hashed = (string)substr(sha1($testcase1),0,10);
  //echo($testcase1."
");
  $findornot = array_search($hashed,$array); 

  if($findornot !== false) {
    $array[$testcase1] = $hashed; 
    echo ($findornot."
"); 
    echo ($testcase1."
"); 
    echo ($hashed);

    $do=false;
  } else {
    $array[$testcase1] = $hashed; 
  }
  //print_r(array_values($array));
}while($do)
?>

Answer 1

TL;DR

$findornot = array_search($hashed, $array, true);

Fixed.

---

Explanation:

You're not going crazy.

The key is "strict comparison" - you've correctly type casted in a few places, and used === for your own comparisons.

You need array_search to do the same thing. Otherwise a string like 0e1 will match 0e2 according to array_search.

The third parameter to array_search is an optional boolean to force strict comparison. Turn that on, and your problem will go away.

---

Update (to prove)

Proof code (input):

<?php
$a = "2e1";
$b = "2e2";

var_dump($a == $b);
var_dump($a === $b);
var_dump($a == "20");
var_dump($a === "20");

Proof output:

bool(false)
bool(false)
bool(true)
bool(false)

PHP is seeing the 'e' character surrounded by numeric digits and is treating it as a exponential when type-juggling to an integer.

It's one of PHP's best features, and one of its greatest failings IMHO. Ah well! Anyone up for coding in C?