/** * Merges two strings in a way that a pattern like ABABAB will be * the result. * * @param string $str1 String A * @param string $str2 String B * @return string Merged string */ function MergeBetween($str1, $str2){ // Split both strings $str1 = str_split($str1, 1); $str2 = str_split($str2, 1); // Swap variables if string 1 is larger than string 2 if (count($str1) >= count($str2)) list($str1, $str2) = array($str2, $str1); // Append the shorter string to the longer string for($x=0; $x < count($str1); $x++) $str2[$x] .= $str1[$x]; return implode('', $str2); } //Example: print MergeBetween('abcdef', '__') . "\n"; print MergeBetween('__', 'abcdef') . "\n"; print MergeBetween('bb', 'aa') . "\n"; print MergeBetween('aa', 'bb') . "\n"; print MergeBetween('a', 'b') . "\n"; /* Output: a_b_cdef a_b_cdef baba abab ab */