I had a problem on how to put dash in every 3rd character. For example, I want 

ABCDEF turn into ABC-DEF

I have this code:

$string = 'ABCDEF';
echo substr_replace(chunk_split($string,3),'-','3','2');
// the output is ABC-DEF

However this code does not work if I add more characters to the $string variable such as ABCDEFGHI. If I use the above code, the output will be:

ABC-DEF GHI
php string replace substr
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