PHP - Need Help With Array Searching

I am including my test.php for other to run.

I have a very large array of concatenated hash values. I have another array that contains the first 8 hash values of the other array. I have a function to locate them in the larger array. Depending on their index value I then choose the index of the value before or behind them for adding to something else later. This 'computeWalk' method works for small arrays but for larger arrays I notice duplicates or errors with larger ones.

For example.

The first array returns:
Array ( => 1 [1] => 18 [2] => 18 [3] => 35 [4] => 33 [5] => 33 )
The values for i's to get each of these values are
I = 0
I = 19
I = 29
I = 34
I = 37
I = 39

Walking through the method by hand,
0%2 = 0
So the first element of the array will be 1. CORRECT.
19%2 = 1
So the next element will be 18. CORRECT.
29%2 = 1
The next element should be 28. It returns 18.
34%2 = 0
The next element will be 35. Correct.
37%2 = 1
The next element should be 36. It returns 33.
39%2 = 1
The next element should be 38. It returns 33.

I am not sure why it's doing the above.
I also tried array_search and it computed it the same way.

Would appreciate any help.


<?php
$arrayTree = array();
$arrayTree[0] = "9d027b1c4068d81287c9170f4b291387f8327eb7";
$arrayTree[1] = "4c8fabdc24c2d8205db916a22e9459195833a272";
$arrayTree[2] = "209526afab9e85b54e1832a820a7f578b7760af0";
$arrayTree[3] = "59d6926525e941edca99493b2b2a4f0a6efcb757";
$arrayTree[4] = "c8b49b8e414a09ddb693c580ecdfa6793c845f9d";
$arrayTree[5] = "b207bea6c4833d90f6ee4e694ffb148c046b0eb3";
$arrayTree[6] = "6d72a84b3aefbd3766078ed17a19aebb0c4ae026";
$arrayTree[7] = "b00207b8944520ea3817334615a7cdbf8214232a";
$arrayTree[8] = "d934f53af9bee26f35df7206dc06211778996986";
$arrayTree[9] = "de2ecd02fd017b0311dbfe589b5faa7954ced196";
$arrayTree[10] = "7d9752d09d3097fac748b6767472f9b69a65ed2e";
$arrayTree[11] = "62630fe109b42747b4c53065ec96aabf7b14d7b6";
$arrayTree[12] = "d727b5b8ffaeadbac75123801c270fd65f19251c";
$arrayTree[13] = "e39a9141fd9ce9426e88f30b6f245fdbb8f887a5";
$arrayTree[14] = "85fe053baa7ccf469c440a7dd98381228a0c52c3";
$arrayTree[15] = "6199634d410d0c91fd6ff99af9eabd5a1c7911de";
$arrayTree[16] = "af594de7d539519445013b7c87f02edbf3c44653";
$arrayTree[17] = "b6eb6dab75d092f4be345925ccbf87ff1e17fc31";
$arrayTree[18] = "2163ca6b0a608242712af82a81599f1f95c26dee";
$arrayTree[19] = "9d027b1c4068d81287c9170f4b291387f8327eb74c8fabdc24c2d8205db916a22e9459195833a272";
$arrayTree[20] = "209526afab9e85b54e1832a820a7f578b7760af059d6926525e941edca99493b2b2a4f0a6efcb757";
$arrayTree[21] = "c8b49b8e414a09ddb693c580ecdfa6793c845f9db207bea6c4833d90f6ee4e694ffb148c046b0eb3";
$arrayTree[22] = "6d72a84b3aefbd3766078ed17a19aebb0c4ae026b00207b8944520ea3817334615a7cdbf8214232a";
$arrayTree[23] = "d934f53af9bee26f35df7206dc06211778996986de2ecd02fd017b0311dbfe589b5faa7954ced196";
$arrayTree[24] = "7d9752d09d3097fac748b6767472f9b69a65ed2e62630fe109b42747b4c53065ec96aabf7b14d7b6";
$arrayTree[25] = "d727b5b8ffaeadbac75123801c270fd65f19251ce39a9141fd9ce9426e88f30b6f245fdbb8f887a5";
$arrayTree[26] = "85fe053baa7ccf469c440a7dd98381228a0c52c36199634d410d0c91fd6ff99af9eabd5a1c7911de";
$arrayTree[27] = "af594de7d539519445013b7c87f02edbf3c44653b6eb6dab75d092f4be345925ccbf87ff1e17fc31";
$arrayTree[28] = "2163ca6b0a608242712af82a81599f1f95c26dee";
$arrayTree[29] = "9d027b1c4068d81287c9170f4b291387f8327eb74c8fabdc24c2d8205db916a22e9459195833a272209526afab9e85b54e1832a820a7f578b7760af059d6926525e941edca99493b2b2a4f0a6efcb757";
$arrayTree[30] = "c8b49b8e414a09ddb693c580ecdfa6793c845f9db207bea6c4833d90f6ee4e694ffb148c046b0eb36d72a84b3aefbd3766078ed17a19aebb0c4ae026b00207b8944520ea3817334615a7cdbf8214232a";
$arrayTree[31] = "d934f53af9bee26f35df7206dc06211778996986de2ecd02fd017b0311dbfe589b5faa7954ced1967d9752d09d3097fac748b6767472f9b69a65ed2e62630fe109b42747b4c53065ec96aabf7b14d7b6";
$arrayTree[32] = "d727b5b8ffaeadbac75123801c270fd65f19251ce39a9141fd9ce9426e88f30b6f245fdbb8f887a585fe053baa7ccf469c440a7dd98381228a0c52c36199634d410d0c91fd6ff99af9eabd5a1c7911de";
$arrayTree[33] = "af594de7d539519445013b7c87f02edbf3c44653b6eb6dab75d092f4be345925ccbf87ff1e17fc312163ca6b0a608242712af82a81599f1f95c26dee";
$arrayTree[34] = "9d027b1c4068d81287c9170f4b291387f8327eb74c8fabdc24c2d8205db916a22e9459195833a272209526afab9e85b54e1832a820a7f578b7760af059d6926525e941edca99493b2b2a4f0a6efcb757c8b49b8e414a09ddb693c580ecdfa6793c845f9db207bea6c4833d90f6ee4e694ffb148c046b0eb36d72a84b3aefbd3766078ed17a19aebb0c4ae026b00207b8944520ea3817334615a7cdbf8214232a";
$arrayTree[35] = "d934f53af9bee26f35df7206dc06211778996986de2ecd02fd017b0311dbfe589b5faa7954ced1967d9752d09d3097fac748b6767472f9b69a65ed2e62630fe109b42747b4c53065ec96aabf7b14d7b6d727b5b8ffaeadbac75123801c270fd65f19251ce39a9141fd9ce9426e88f30b6f245fdbb8f887a585fe053baa7ccf469c440a7dd98381228a0c52c36199634d410d0c91fd6ff99af9eabd5a1c7911de";
$arrayTree[36] = "af594de7d539519445013b7c87f02edbf3c44653b6eb6dab75d092f4be345925ccbf87ff1e17fc312163ca6b0a608242712af82a81599f1f95c26dee";
$arrayTree[37] = "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";
$arrayTree[38] = "af594de7d539519445013b7c87f02edbf3c44653b6eb6dab75d092f4be345925ccbf87ff1e17fc312163ca6b0a608242712af82a81599f1f95c26dee";
$arrayTree[39] = "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";
$arrayTree[40] = "54u58rfhfheyrr4gfdtfvgw36tr36";
$arrayTree[41] = "54u58rfhfheyrr4gfdtfvgw36tr369d027b1c4068d81287c9170f4b291387f8327eb74c8fabdc24c2d8205db916a22e9459195833a272209526afab9e85b54e1832a820a7f578b7760af059d6926525e941edca99493b2b2a4f0a6efcb757c8b49b8e414a09ddb693c580ecdfa6793c845f9db207bea6c4833d90f6ee4e694ffb148c046b0eb36d72a84b3aefbd3766078ed17a19aebb0c4ae026b00207b8944520ea3817334615a7cdbf8214232ad934f53af9bee26f35df7206dc06211778996986de2ecd02fd017b0311dbfe589b5faa7954ced1967d9752d09d3097fac748b6767472f9b69a65ed2e62630fe109b42747b4c53065ec96aabf7b14d7b6d727b5b8ffaeadbac75123801c270fd65f19251ce39a9141fd9ce9426e88f30b6f245fdbb8f887a585fe053baa7ccf469c440a7dd98381228a0c52c36199634d410d0c91fd6ff99af9eabd5a1c7911deaf594de7d539519445013b7c87f02edbf3c44653b6eb6dab75d092f4be345925ccbf87ff1e17fc312163ca6b0a608242712af82a81599f1f95c26dee";


$arrayDocs = array();
$arrayDocs[0] = "9d027b1c4068d81287c9170f4b291387f8327eb7";
$arrayDocs[1] = "4c8fabdc24c2d8205db916a22e9459195833a272";
$arrayDocs[2] = "209526afab9e85b54e1832a820a7f578b7760af0";
$arrayDocs[3] = "59d6926525e941edca99493b2b2a4f0a6efcb757";
$arrayDocs[4] = "c8b49b8e414a09ddb693c580ecdfa6793c845f9d";
$arrayDocs[5] = "b207bea6c4833d90f6ee4e694ffb148c046b0eb3";
$arrayDocs[6] = "6d72a84b3aefbd3766078ed17a19aebb0c4ae026";
$arrayDocs[7] = "b00207b8944520ea3817334615a7cdbf8214232a";
$arrayDocs[8] = "d934f53af9bee26f35df7206dc06211778996986";
$arrayDocs[9] = "de2ecd02fd017b0311dbfe589b5faa7954ced196";
$arrayDocs[10] = "7d9752d09d3097fac748b6767472f9b69a65ed2e";
$arrayDocs[11] = "62630fe109b42747b4c53065ec96aabf7b14d7b6";
$arrayDocs[12] = "d727b5b8ffaeadbac75123801c270fd65f19251c";
$arrayDocs[13] = "e39a9141fd9ce9426e88f30b6f245fdbb8f887a5";
$arrayDocs[14] = "85fe053baa7ccf469c440a7dd98381228a0c52c3";
$arrayDocs[15] = "6199634d410d0c91fd6ff99af9eabd5a1c7911de";
$arrayDocs[16] = "af594de7d539519445013b7c87f02edbf3c44653";
$arrayDocs[17] = "b6eb6dab75d092f4be345925ccbf87ff1e17fc31";
$arrayDocs[18] = "2163ca6b0a608242712af82a81599f1f95c26dee";


foreach($arrayDocs as $doc) {
 $bitIndex = computeWalk($arrayTree, $doc);
 echo "<br/>";
        print_r($bitIndex);

echo "<br/>";
}

function computeWalk($array, $needle) {
    $result = array();

    for ($i = 0; $i < count($array) - 1; $i++) {
        if (false !== strpos($array[$i], $needle)) {

 echo " I = ".$i;
            if ($i % 2 == 0) {
                $result[] = getItemIndex($array[$i + 1], $array);
            } else {
                $result[] = getItemIndex($array[$i - 1], $array);
            }
        }
    }
    return $result;
}


function getItemIndex($item, $array) {
$myPosition=-1;
for ($i = 0; $i<count($array)-1; $i++) {
if($array[$i]==$item) {
$myPosition = $i;
break;
}
}
return $myPosition;
}
?>