Executing MySQL Queries and Creating Instances several Times within Loop - php

Question

I have an Web Application that requires SELECT and INSERT Querying to MySQL database and Instantiating a PHP class using new operator almost more that thousand times within a loop. May be there are alternatives to my present logic, but my point is that is there any harm if I carry on this logic?. I don't bother about the time complexity associated with the algorithm presently but **worrying much about if anything goes wrong during transaction or memory usage. I am giving the piece of code for reference
$stm_const = "select ce.TIMETAKEN, qm.QMATTER as STRING1, ce.SMATTER as STRING2 from w_clkexam ce, clkmst cm, qsmst qm where ce.QID=qm.QID and cm.ROLLNO=ce.ROLLNO";
for ($c=0; $c < count($rollnos); $c++) {
$stm3 =$stm_const." "."and ce.ROLLNO='$rollnos[$c]'";
$qry3 = mysql_query($stm3) or die("ERROR 3:".mysql_error());
while($row1 = mysql_fetch_array($qry3)) {
echo $string1=$row1['STRING1'];
echo $string2=$row1['STRING2'];
$phpCompareStrings=new PhpCompareStrings($string2, $string1);
$percent=$phpCompareStrings->getSimilarityPercentage();
$percent2=$phpCompareStrings->getDifferencePercentage();
echo '$string1 and $string2 are '.$percent.'% similar and '.$percent2.'% differnt<br/>';
}// end while
}// end for
Please help, I am waiting for opinions from you so that I can move further. Thanks in advance.

Answer 1

I don't see any problem there. You just get all the rows from database and for each row compare the strings. As you assign the object to the same variable each time, the old object is destroyed before the new object is created. So you have only one instance of the object in memory at all times. The question is what you want to do with the results? Only print them as in your example, or to store the results for further processing?
Anyway, I think it is not possible to optimize your code without modifying the class. If you are using this class, you can try to modify it so that it can accept multiple strings. Using this, you can create only 1 instance of the class and you avoid destroying/creating the object for every row. It will save you some CPU time, but not memory (as at all times, only 1 instance of the class is active).
Untested modification below:
Modify this function inside the class:
function __construct($str1,$str2){
$str1=trim($str1);
$str2=trim($str2);
if($str1==""){ trigger_error("First parameter can not be left blank", E_USER_ERROR); }
elseif($str2==""){ trigger_error("Second parameter can not be left blank", E_USER_ERROR); }
else{
$this->str1=$str1;
$this->str2=$str2;
$this->arr1=explode(" ",$str1);
$this->arr2=explode(" ",$str2);
}
}
To these 2 functions:
function init($str1,$str2){
$str1=trim($str1);
$str2=trim($str2);
if($str1==""){ trigger_error("First parameter can not be left blank", E_USER_ERROR); }
elseif($str2==""){ trigger_error("Second parameter can not be left blank", E_USER_ERROR); }
else{
$this->str1=$str1;
$this->str2=$str2;
$this->arr1=explode(" ",$str1);
$this->arr2=explode(" ",$str2);
}
}
function __construct($str1,$str2){ $this->init($str1,$str2); }
Then create the object outside the loop and only call $phpCompareStrings->init($string2,$string1) inside the loop.