PHP strings vs array errors

I will add the actual data files if needed but for now I need to see if anything is wrong with code.

I am returning results from a curl session where it looks though and tries to match any URLs in the file, so I do this.

I save the results in the curl session as follows,

file_put_contents("../textfiles/$curlResponse.txt",serialize($response));

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(I need to save the results to a file because I will need to reference it more than once after leaving the page and I don't want to have to redundantly make curl connections when I can just use a file that was already generated earlier.)

Later on, when trying use the data, I am scanning for specific URL's so I do this...

//put the file back into a variable to work with

$response2=unserialize(trim(file_get_contents("../textfiles/$curlResponse.txt")));

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//Find all URL's on page

preg_match_all('/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i',$response2,$match);

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//remove duplicates

$urlResults=array_map('array_unique', $match);

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At this point when I view the $match or the $urlResults all looks fine.  I have a list of non duplicated URLS as expected but here is where I have the problem.

Something went funky and the array ends up getting stored inside another array.  I don't know enough about the how and why it happened but I don't need my array needlessly stored inside another blank array and furthermore don't understand enough about how to access what I need without making it one clean array.

$urlResults=$urlResults[0]; 

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I am now trying to loop over the refined results and categorize them so I did this

foreach($urlResults as $k=>$v){
         if(someCondition){
        $finalURL[]=$v;
}elseif(someOtherCondition){
	$finalUR2L[]=$v
	}
}

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and I get this....

Uncaught Error: [] operator not supported for strings

and the weirdest part is this... remember how I said I have it stored in a file?  

There is an include on the page to use the cURL script to create the file that will be used if its NOT in existence.

If it runs the include, I get the error I have shown above.  The next time its run and all subsequent tries it works fine, and its the same exact code,file, and page!  It seems there is some issue with trying to use the data from the file immediately after creating it? Only difference is in one case it was diverted to the curl script where it creates and uses the file immediately (fails), whereas all other future requests will have no need to run through the curl include (succeeds by using the file that was created and gave an error the first time!!!)

Is there some rule about not doing anything else on a page that uses cURL?  If the file will work on try 2, why won't it work on try 1??? Its the same code, same page and same file, with the only difference being whether the cURL script was freshly run to create it, or if it bypassed the cURL function because it found the file...