explode a:b to a:c php - php

Question

I have 2 files for example
file1.txt
and
file2.txt
file1.txt contains for example following content:
a:b
markus:lanz
peter:heinrichs
lach:schnell
and file2.txt contains for example following content (the 2nd explode of the file1.txt)
b:c
lanz:hallo
heinrichs:gruss
schnell:langsam
so i want to have following output in php:
a:c
markus:hallo
peter:gruss
lach:langsam
how is this possible?
first explode the first and then search or how?
thanks
my current code is following:
<?php
$file1 = 'a:b
markus:lanz
peter:heinrichs
lach:schnell';
$file2 = '
lanz:hallo
heinrichs:gruss
b:c
test:notest
schnell:langsam';
$array = explode(":", $file1);
for($i=0; $i < count($array); $i++) {
$array = explode(":", $file1);
$pattan = $array[$i];
$pattern = '=\n'. $pattan .':(.*)\n=sUm';
$result = preg_match($pattern, $file2, $subpattern);
echo "<br>";
echo $array[$i];
$first = $array[$i];
echo "<br>";
}
$pattern = '=\n'. $first .':(.*)\n=sUm';
$result = preg_match($pattern, $file2, $subpattern);
var_dump($subpattern);
?>
what am i making wrong?

Answer 1

What do you think about this :
$file1="a:b
markus:lanz
peter:heinrichs
lach:schnell";
$file2="b:c
lanz:hallo
heinrichs:gruss
schnell:langsam";
$a1 = explode("\n",$file1);
$a2 = explode("\n",$file2);
if(count($a1) != count($a2)) die("files don't match!");
$final=array();
foreach($a1 as $k=>$line){
$l1 = explode(":",$line);
$l2 = explode(":",$a2[$k]);
$final[]=$l1[0].':'.$l2[1];
}
print_r($final);

Answer 2

I would use the following approach:
// load your two files into arrays using file() and explode each line on ':'
foreach ([1,2] as $n) {
$files[$n] = array_map(function($x){ return explode(':', trim($x));}, file("file$n.txt"));
}
// with file1, fill the output array with 'a' values using 'b' as the key to output
foreach ($files[1] as $ab) {
$output[$ab[1]]['a'] = $ab[0];
}
// with file2, fill the output array with 'c' values, also using 'b' as the key
foreach ($files[2] as $bc) {
$output[$bc[0]]['c'] = $bc[1];
}
// remove any elements that do not have count 2 (i.e. both a and c values)
$output = array_filter($output, function ($x) { return count($x) == 2; });