2个数组相同的键和值检查来自一个数组的值是否在这里

I have 2 arrays merge to one array, Now i want to check if value 1 in array $b then add special content value to $b in foreach.

But in below example added the content to $s and $b

$s = array(1,2,3,4,5);
$b = array(1,2,3,4);

 $one = array_merge($s,$b);
 $arr = array_chunk($one, 1);
foreach($arr as $k=>$v){
if(in_array($arr[$k][0],$b)){
    echo "c";
}
     echo $arr[$k][0]."<br>";
}

Output

c1
c2
c3
c4
5
c1
c2
c3
c4

And i want that output

1
2
3
4
5
c1
c2
c3
c4

It's Simple. You just have to check with the if condition. If the loop has been repeated more than the length of the array $s, then do echo "c";

$s = array(1,2,3,4,5);
$b = array(1,2,3,4);

$one = array_merge($s,$b);
$arr = array_chunk($one, 1);
$s_length = count($s);
$i = 1;
foreach($arr as $k=>$v){
    // Check if the loop has been repeated more than the length of the array $s
    if($i > $s_length){
        echo "c";
    }
    echo $arr[$k][0]."<br>";
    $i++;
}

I don't know exactly if that is what you want but:

$s = array(1,2,3,4,5);
$b = array(1,2,3,4);

$arr = array_diff($s, $b);

// Search differences between diff() and $s
$cs= "";
$cb= "";
// If array have semantical keys we'll do an array_values()
foreach ( array_values($arr) as $k => $v ){ 
    // If $cs is actually set as 'c'
    if ( "c"!=$cs ){
        // If a value in the diff() array are not in s => $cs = 'c'
        $cs= ( !in_array( $v, $s ,true ))? "c": "";
    }
    // If $cb is actually set as 'c'
    if ( "c"!=$cb ){
        $cb= ( !in_array( $v, $b ,true ))? "c" : "";
    }
}

// Print each array values with associated $c
foreach ( $s as $k => $v ){ 
    echo "<br>$cs$v"    ;
}
foreach ( $b as $k => $v ){ 
    echo "<br>$cb$v"    ;
}

Output:

1
2
3
4
5
c1
c2
c3
c4