PHP array combination with order

Question

I'm trying to figure out how to combine two arrays while keeping the order of each separate array in PHP.

Here is a example

$array1=array("a","b","c","d"); a needs to be before b, b needs to be before c, c needs to be before d $array2=array("h","g","f","e"); h needs to be before g, g needs to be before f,f needs to be before e

All elements needs to be there so the output will always contain the sum of all elements.

In the end, I'd like to get all combos like:

h,g,f,e,a,b,c,d
h,g,f,a,e,b,c,d
h,g,f,a,b,e,c,d
h,g,f,a,b,c,e,d
h,g,f,a,b,c,d,e

h,g,a,f,e,b,c,d
h,g,a,f,b,e,c,d
h,g,a,f,b,c,e,d
h,g,a,f,b,c,d,e

h,g,a,b,f,e,c,d
h,g,a,b,f,c,e,d
h,g,a,b,f,c,d,e

...etc...

I have found many examples for combinations on this site but none where the output should keep the initial order.

Do you have any idea of how I might do it? I can do it iteratively but given all the combinations, it's clearly not the best way to go.

Thanks Laurent

I don't really understand your question. You want to keep the order but you also want every possible order combination? — Joel Hinz
– Joel Hinz, Commented Jan 18, 2015 at 20:27
I'm looking to mix arrays with all possible combinations but the order of the initial array should be respected. Hellcode here below has found a solution. Thanks — Laurent
– Laurent, Commented Jan 19, 2015 at 19:06

hellcode · Accepted Answer · 2015-01-18 20:57:58Z

Here is my suggestion for a script:

<?php

  $array1 = array("a","b","c","d");
  $array2 = array("h","g","f","e");
  // produce 8-byte-string with each 4 values of array 1 and 2
  // looks like a byte with 8 bits of value 0 and 1
  // and delete combinations with other than 4 zeroes and 4 ones
  $combos = array();
  for($i=0; $i<256; $i++) {
    $str = decbin($i);
    $str = substr("00000000",0,8-strlen($str)).$str;
    // just check if there are 4 ones in the string
    if(strlen(str_replace("0","",$str))==4) {
      // then add it to combos array
      $combos[$str] = array();
      // echo it if you like
      //echo "<br>".$i.": ".$str;
    }
  }
  # now you have all combinations
  # so you can fill it with the array values
  foreach($combos as $key => $array) {
    $array = array();
    $x1=0;
    $x2=0;
    for($i=0; $i<strlen($key); $i++) {
      if(substr($key,$i,1) == "1") {
        $array[] = $array1[$x1];
        $x1++;
      } else {
        $array[] = $array2[$x2];
        $x2++;
      }
    }
    // echo it if you like
    echo "<br>".$key.": ".implode(", ",$array);
    $combos[$key] = $array;
  }
  echo "<br /><br />Combinations: ".count($combos);

?>

And here is the output:

00001111: h, g, f, e, a, b, c, d
00010111: h, g, f, a, e, b, c, d
00011011: h, g, f, a, b, e, c, d
00011101: h, g, f, a, b, c, e, d
00011110: h, g, f, a, b, c, d, e
00100111: h, g, a, f, e, b, c, d
00101011: h, g, a, f, b, e, c, d
00101101: h, g, a, f, b, c, e, d
00101110: h, g, a, f, b, c, d, e
00110011: h, g, a, b, f, e, c, d
00110101: h, g, a, b, f, c, e, d
00110110: h, g, a, b, f, c, d, e
00111001: h, g, a, b, c, f, e, d
00111010: h, g, a, b, c, f, d, e
00111100: h, g, a, b, c, d, f, e
01000111: h, a, g, f, e, b, c, d
01001011: h, a, g, f, b, e, c, d
01001101: h, a, g, f, b, c, e, d
01001110: h, a, g, f, b, c, d, e
01010011: h, a, g, b, f, e, c, d
01010101: h, a, g, b, f, c, e, d
01010110: h, a, g, b, f, c, d, e
01011001: h, a, g, b, c, f, e, d
01011010: h, a, g, b, c, f, d, e
01011100: h, a, g, b, c, d, f, e
01100011: h, a, b, g, f, e, c, d
01100101: h, a, b, g, f, c, e, d
01100110: h, a, b, g, f, c, d, e
01101001: h, a, b, g, c, f, e, d
01101010: h, a, b, g, c, f, d, e
01101100: h, a, b, g, c, d, f, e
01110001: h, a, b, c, g, f, e, d
01110010: h, a, b, c, g, f, d, e
01110100: h, a, b, c, g, d, f, e
01111000: h, a, b, c, d, g, f, e
10000111: a, h, g, f, e, b, c, d
10001011: a, h, g, f, b, e, c, d
10001101: a, h, g, f, b, c, e, d
10001110: a, h, g, f, b, c, d, e
10010011: a, h, g, b, f, e, c, d
10010101: a, h, g, b, f, c, e, d
10010110: a, h, g, b, f, c, d, e
10011001: a, h, g, b, c, f, e, d
10011010: a, h, g, b, c, f, d, e
10011100: a, h, g, b, c, d, f, e
10100011: a, h, b, g, f, e, c, d
10100101: a, h, b, g, f, c, e, d
10100110: a, h, b, g, f, c, d, e
10101001: a, h, b, g, c, f, e, d
10101010: a, h, b, g, c, f, d, e
10101100: a, h, b, g, c, d, f, e
10110001: a, h, b, c, g, f, e, d
10110010: a, h, b, c, g, f, d, e
10110100: a, h, b, c, g, d, f, e
10111000: a, h, b, c, d, g, f, e
11000011: a, b, h, g, f, e, c, d
11000101: a, b, h, g, f, c, e, d
11000110: a, b, h, g, f, c, d, e
11001001: a, b, h, g, c, f, e, d
11001010: a, b, h, g, c, f, d, e
11001100: a, b, h, g, c, d, f, e
11010001: a, b, h, c, g, f, e, d
11010010: a, b, h, c, g, f, d, e
11010100: a, b, h, c, g, d, f, e
11011000: a, b, h, c, d, g, f, e
11100001: a, b, c, h, g, f, e, d
11100010: a, b, c, h, g, f, d, e
11100100: a, b, c, h, g, d, f, e
11101000: a, b, c, h, d, g, f, e
11110000: a, b, c, d, h, g, f, e

Combinations: 70

hellcode, this is brilliant! Exactly what I need and elegant solution! Thanks a lot

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