Differences between 2 strings

[Aravinthan]

Hi,

 

I was wondering how to do a script that finds the difference between 2 strings and outputs it.

 

Exemple:

 

string1 = "This is a test";

string 2 = "This was a testing";

 

Ouput should be:

 

String 1: is

Strng 2: was

 

String 1:test

String 2: testing

 

 

Thanks for your help,

 

Ara

[5kyy8lu3]

you could explode(" ", $string1); the string using space then compare the items in your arrays

[yettti]

Given that both strings are the same length this would do it...

(it even lays it out like you did... but without the spelling mistake )

 

$string1 = "this is a test";
$string2 = "this was a testing";

$string1 = explode(" ",$string1);
$string2 = explode(" ",$string2);
foreach ($string1 as $key => $value) {
if ($value != $string2[$key]) {
	echo "String 1 : ".$value;
	echo "<br>String 2 : ".$string2[$key]."<br><br>";
}
}

 

... little explination,

$string1 = explode(" ",$string1);
$string2 = explode(" ",$string2);

This splits the strings into arrays, it splits them by a space

 

foreach ($string1 as $key => $value) {

This then loops through all the items in the array $string1 and assigns the current key and value to variables.

 

if ($value != $string2[$key]) {

This checks to see if there not the same...

 

echo "String 1 : ".$value;
echo "<br>String 2 : ".$string2[$key]."<br><br>";

and if so prints them out!

[Aravinthan]

Hi thanks for your help guys.

 

Yetti, thank you but I get this error:

Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 2097152 bytes) in /home/liguehs/public_html/converter/test_players.php on line 140014

 

The 2 strings are pretty big... if I put them in a separate file, they have around 1 500 000 Kilobytes....

 

Is there a work around?

 

Thanks for your help,

Ara

[yettti]

Ok.. what your getting there is a error showing that too much memory has been used, because you are reading from a large file... to do it from a large file is a bit different.

It can be done... but it would depend on how the file is formated?

[Aravinthan]

OK I uploaded a file( the whole file is a string )

 

It was too big to be uploaded on the forums.

 

Link:

http://www.megafileupload.com/en/file/134577/players-txt.html

[yettti]

Ok, in that case i would advise that you read the file line by line comparing the string on each line, that way you don't end up trying to load the entire file into the variables, instead you load each line, overwriting the last line each loop

 

this... should work, although i haven't tested it

$file1 = fopen("doc1.txt", "r");
$file2 = fopen("doc2.txt", "r");
while(!feof($file1 || $file2)) {
$string1 = explode(" ",$string1);
$string2 = explode(" ",$string2);
foreach ($string1 as $key => $value) {
	if ($value != $string2[$key]) {
		echo "String 1 : ".$value;
		echo "<br>String 2 : ".$string2[$key]."<br><br>";
	}
}
}
fclose($file);

[Aravinthan]

Hi,

Thanks for your help,

 

But I get the following error:

Warning: feof(): supplied argument is not a valid stream resource in /home/liguehs/public_html/converter/test_players.php on line 4

 

[yettti]

Oh... sorry, my mistake

it should be

$file1 = fopen("doc1.txt", "r");
$file2 = fopen("doc2.txt", "r");
while(!feof($file1) || !feof($file2))) {
$string1 = explode(" ",$string1);
$string2 = explode(" ",$string2);
foreach ($string1 as $key => $value) {
	if ($value != $string2[$key]) {
		echo "String 1 : ".$value;
		echo "<br>String 2 : ".$string2[$key]."<br><br>";
	}
}
}
fclose($file);

 

Made a mistake on the while loop condition. see how i works

[Zyx]

It will not work, because you forgot about reading from a file . Anyway, the presented algorithm is too simple and covers only the easiest cases. For example:

 

foo bar joe aaa bbb ccc

foo lol bar joe aaa bbb ccc

 

The difference is the extra word, but the algorithm will show that the whole string from this place is different.

 

http://www.xmailserver.org/diff2.pdf

 

Here you have a description of the algorithm used in the Linux diff program.

[Aravinthan]

Hi I get this error now:

Fatal error: Maximum execution time of 20 seconds exceeded in /home/liguehs/public_html/converter/test_players.php on line 6

[yettti]

Cant do much to help you there . This is  because you are trying to process a too larger file and the server stops a single script after 20 seconds. you can change this in your php.ini file

[Aravinthan]

Isnt there a way of giving it a reste? Like mysql rest for exemple?

 

I cant change the php.ini file... my host doesnt allow it.

[Daniel0]

You can use set_time_limit.

[Aravinthan]

So I put set_time_limit(20) before my script?

[kingnutter]

Have a look into array_diff. It might work for you.

[Aravinthan]

You mean that I explode my files using line breaks, and then I put them in a while loop to run 1 line at a time?

[Daniel0]

So I put set_time_limit(20) before my script?

 

If you read the man page you'll find out.

[mikesta707]

$string1 = "this is a test";
$string2 = "this was a testing";

$string1 = explode(" ",$string1);
$string2 = explode(" ",$string2);
foreach ($string1 as $key => $value) {
if ($value != $string2[$key]) {
	echo "String 1 : ".$value;
	echo "<br>String 2 : ".$string2[$key]."<br><br>";
}
}

 

unless you are trying to see if a string is exactly the same, this won't work. if you want to take a string, and compare each word and see which words are different, I suggest you do a string explode, and use the array_diff function.

 

As far as your files problems, if you can't change php.ino then you probably want to set a time limit of more than 20, like 30 seconds or something.