拆分字符串[关闭]

I have created an encryption algorithm in which I need to reverse, I need to separate a string into pairs of 3 into an array, I have looked all over and have found no help, how would I do this?

Edit: I have tried:

<?php
$todecode="#number too big to post#";
$len=strlen($todecode);
$a=0;
$b=array();
While($len!=$a){
//$decoded=chunk_split($todecode);
$add1=$todecode[$a];
$a=$a+1;
$add2=$todecode[$a];
$a=$a+1;
$add3=$todecode[$a];
$a=$a+1;
$adder=$add1,$add2,$add3;
array_push($b,$adder);
}

But nothing else yet.

    $num_str = "12312312315234535";
    print_r(str_split($num_str,3));

I don't know PHP, but I can provide a suggestion on what you must do.

First, you need to count the characters of your string, and create the 3 cell arrays you need:

• If you string has 19 chars, then you will need ceil(19 / 3) = 7 arrays, or (better) a 7-by-3 array

Then you'll need to store the chars on every row of the array:

i = -1; j=0;
for(j=0; j<length_of_your_string; j++) {
    if (j % 3 == 0)
        i++;
    result_array[i][j % 3] = your_string.charAt(j);
}

I leave to you the translation to something you can use.