built in function to combine overlapping string sequences in php? - php

Question

Is there a built in function in PHP that would combine 2 strings into 1?
Example:
$string1 = 'abcde';
$string2 = 'cdefg';
Combine to get: abcdefg.
If the exact overlapping sequence and the position are known, then it is possible to write a code to merge them.
TIA

Answer 1

I found the substr_replace method to return funny results.
Especially when working with url strings. I just wrote this function.
It seems to be working perfectly for my needs.
The function will return the longest possible match by default.
function findOverlap($str1, $str2){
$return = array();
$sl1 = strlen($str1);
$sl2 = strlen($str2);
$max = $sl1>$sl2?$sl2:$sl1;
$i=1;
while($i<=$max){
$s1 = substr($str1, -$i);
$s2 = substr($str2, 0, $i);
if($s1 == $s2){
$return[] = $s1;
}
$i++;
}
if(!empty($return)){
return $return;
}
return false;
}
function replaceOverlap($str1, $str2, $length = "long"){
if($overlap = findOverlap($str1, $str2)){
switch($length){
case "short":
$overlap = $overlap[0];
break;
case "long":
default:
$overlap = $overlap[count($overlap)-1];
break;
}
$str1 = substr($str1, 0, -strlen($overlap));
$str2 = substr($str2, strlen($overlap));
return $str1.$overlap.$str2;
}
return false;
}
Usage to get the maximum length match:
echo replaceOverlap("abxcdex", "xcdexfg"); //Result: abxcdexfg
To get the first match instead of the last match call the function like this:
echo replaceOverlap("abxcdex", "xcdexfg", “short”); //Result: abxcdexcdexfg
To get the overlapping string just call:
echo findOverlap("abxcdex", "xcdexfg"); //Result: array( 0 => "x", 1 => "xcdex" )

Answer 2

It's possible using substr_replace() and strcspn():
$string1 = 'abcde';
$string2 = 'cdefgh';
echo substr_replace($string1, $string2, strcspn($string1, $string2)); // abcdefgh

Answer 3

No, there is no builtin function, but you can easily write one yourself by using substr and a loop to see how much of the strings that overlap.