Check if substring of a string is substring of another string

Question

I have two strings

$Str1 = "A B C D E F G H I J";
$Str2 = "1 2 C D E P Q R";

Now I have to check that a substring of $Str2 exits in $Str1. For example in this case C D E.

This is a basic and simple example. I am having complex cases and data in both strings is dynamic.

If I would had to compare complete string the strpos was the solution but what to do in this case?

Does order matter? Is a char in a different location still a match? Do you need to return the specific chars and their locations? What about space chars - they clearly exist in both strings, but im guessing you dont count those? Is a single char a match, or do you need to find strings with a minimum length? As it stands this question is too vague to answer — Steve
– Steve, Commented Oct 14, 2015 at 14:00
@Steve, Position doesn't matter. I just need if substring of string exits as a substring in other string. And I have to match complete word(s). This is a basic example, I am having actual text in both strings. In my string there won't be chars but words and two words of a string should be together in other string if I am checking for those two words. — Gulfam
– Gulfam, Commented Oct 14, 2015 at 14:07
Ok well perhaps you need to edit your question with a more realistic example, because at the moment its really unclear. — Steve
– Steve, Commented Oct 14, 2015 at 14:11

Kanti · Accepted Answer · 2015-10-14 14:23:22Z

2

This function should work any Strings

function test($str1, $str2)
{
    for ($i = strlen($str1); $i != 0; $i--) {
        for ($x = 0; $x < strlen($str1) - $i; $x++) {
            if (($pos = strpos($str2, substr($str1, $x, $i + 1))) !== false) {
                return substr($str1, $x, $i + 1);
            }
        }
    }
    return null;
}

It returns the biggest possible match or null.

$str1 = "Sed ut perspiciatis unde omnis iste natus error sit voluptatem";
$str2 = "Sed ut perspiciatis undeT omnis iste natus error sit voluptatem";
echo test($str1, $str2); // omnis iste natus error sit voluptatem

edited Oct 14, 2015 at 14:23

answered Oct 14, 2015 at 14:11

Kanti

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1 Comment

Gulfam Over a year ago

Thanks, Just what I required.

Daan · Accepted Answer · 2015-10-14 14:06:21Z

1

This function should work for you:

<?php
$Str1 = "A B C D E F G H I J";
$Str2 = "1 2 C D E P Q R";

echo strCompare($Str1, $Str2); //Returns C D E

function strCompare($Str1, $Str2) {
    $str1 = explode(" ", $Str1);
    $str2 = explode(" ", $Str2);

    $match = false;
    $newStr = [];

    foreach($str1 as $key => $value){
        if($match == true){
            if(isset($str2[$key]) && $str2[$key] == $value){
                $newStr[] = $value;
            } else {
                break;
            }
        } else {
            if(isset($str2[$key]) && $str2[$key] == $value){
                $match = true;
                $newStr[] = $value;
            }   
        }
    };

    return implode(" ",$newStr);

}

answered Oct 14, 2015 at 14:06

Daan

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2 Comments

Gulfam Over a year ago

I tried but it was not working. Solution provided by Kanti worked exactly in the way I required. Thanks for the help though :)

Daan Over a year ago

If this doesn't work then you have a very old PHP version (PHP 5.4<). You should upgrade it.

dkr · Accepted Answer · 2015-10-14 21:51:16Z

maybe this one might help too:

<?php
/**
 * returns an array of positions and substrings of needle that were found 
 * in string haystack using a minimal and maximal substring length
 * 
 * @param unknown $haystack find substrings of needle in this string
 * @param unknown $needle substrings in needle will be searched in haystack
 * @param number $min minimal length of a substring
 * @param number $max maximum length of a substring
 * @return array empty if no result
 */
function intersect_string($haystack,$needle,$min=3,$max=25)
{
    $r = [];
    for($j=$i=0;isset($needle[$i])&&isset($needle[$i+1]);$j=0,$i++) {
        if (!($c=$needle[$i].$needle[$i+1])) continue;
        while (($p=strpos($haystack,$c,$j))!==false) {
            $r[$p] = $c;
            for ($j=$p+2,++$i;isset($needle[$i+1])&&isset($haystack[$j]);$j++,$i++) {
                if (!($needle[$i+1]==$haystack[$j])) break;
                $r[$p] .= $haystack[$j];
            }
            $l = strlen($r[$p]);
            if ($l<$min||$l>$max) { unset($r[$p]); }
        }
    }
    return $r;
}
header('Content-Type:text/plain');
$str1 = "A little wolf is jumping over the tiny cow";
$str2 = "A tiny cow is jumping over the little wolf";
var_dump(intersect_string($str1,$str2,2));
var_dump(intersect_string($str1,$str2,3,12));
$str1 = "A B C D E F G H I J";
$str2 = "1 2 C D E P Q R";
var_dump(intersect_string($str1,$str2,1));
var_dump(intersect_string($str1,$str2,8));
$str1 = "Sed ut perspiciatis unde omnis iste natus error sit voluptatem";
$str2 = "Sed ut perspiciatis undeT omnis iste natus error sit voluptatem";
var_dump(intersect_string($str1,$str2,3,40));
?>

this will result in:

array(4) {
  [0]=>
  string(2) "A "
  [34]=>
  string(8) "tiny cow"
  [13]=>
  string(21) " is jumping over the "
  [2]=>
  string(11) "little wolf"
}
array(2) {
  [34]=>
  string(8) "tiny cow"
  [2]=>
  string(11) "little wolf"
}
array(1) {
  [3]=>
  string(7) " C D E "
}
bool(false)
array(2) {
  [0]=>
  string(24) "Sed ut perspiciatis unde"
  [24]=>
  string(38) " omnis iste natus error sit voluptatem"
}

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