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Help refactoring if/elseif

Posted on 2010-11-23
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Last Modified: 2012-08-13
I have the code below written by someone else. It is a little confusing
and I would like to refactor it to look better and be more logical.

The SQL has been changed slightly to mask what it is really doing, it is
just the if/elesif's that I am concerned about because the whole construct
looks confusing.

From what I'm seeing, the code inside the "if($cat != "")" inside the elseif's
at lines 8, 15 and 22 will never run because of the first "if($cat != "")" at
line 1. i.e. if $flag == 1 and $cat == 'book' then it would always fall into
the first if at line 1 and never reach the sql at line 9.

Is this a correct assumption?

How would you refactor this code?

 1  if($cat != "") {
 2    $sel_gig="SELECT * FROM table 
 3              WHERE category_id=".$cat;
 4  } elseif($mny != "") {
 5    $sel_gig="SELECT * FROM table 
 6              WHERE price=".$mny
 7  } elseif($flag == "l") {
 8    if($cat != "") {
 9      $sel_gig="SELECT * FROM table 
10                WHERE category_id=".$cat;
11    } else {
12      $sel_gig="SELECT * FROM table";
13    }
14  } elseif($flag == "p") {
15    if($cat != "") {
16      $sel_gig="SELECT * FROM `clientorder`
17                WHERE category_id=".$cat";
18    } else {
19      $sel_gig="SELECT * FROM `clientorder`:;
20    }
21  } elseif($flag == "r11") {
22    if($cat != "") {
23      $sel_gig="SELECT * FROM `feedback`
24                WHERE category_id=".$cat;
25    } else {
26      $sel_gig="SELECT * FROM `feedback`";
27    }
28  }

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Question by:EddieShipman
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9 Comments
 
LVL 3

Expert Comment

by:chrios
ID: 34197231
You can remove all elseif ($cat != "") since that condition is handled on the first line.

That leaves the code below. Maybe you want to add a final else to the list, but this is the cleaned up version.
if($cat != "") {
    $sel_gig="SELECT * FROM table WHERE category_id=".$cat;
 } elseif($mny != "") {
   $sel_gig="SELECT * FROM table WHERE price=".$mny
 } elseif($flag == "l") {
     $sel_gig="SELECT * FROM table";
 } elseif($flag == "p") {
     $sel_gig="SELECT * FROM `clientorder`:;
 } elseif($flag == "r11") {
     $sel_gig="SELECT * FROM `feedback`";
 }

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0
 
LVL 3

Expert Comment

by:chrios
ID: 34197269
Perhaps I should clarify my last post.

Since line 1 is "if($cat != "") {..." you know that in the rest of the elseif-code that condition must be False, therefor you can remove all the "if($cat != "") { xxx } " that follows in the code since it's redundant.
0
 
LVL 26

Author Comment

by:EddieShipman
ID: 34197270
Well, I don't think I can do that. here's the whole code, with different column, table names.
if($cat != "") {
    $sel_table="SELECT * FROM table 
              WHERE category_id=".$cat." 
              LIMIT $start,$max";
  } elseif($mny != "") {
    $sel_table="SELECT * FROM  table 
              WHERE table_price=".$mny." 
              LIMIT $start,$max";
  } elseif($flag == "l") {
    if($cat != "") {
      $sel_table="SELECT * FROM  table 
                WHERE category_id=".$cat." 
                ORDER BY id_col DESC LIMIT $start,$max";
    } else {
      $sel_table="SELECT * FROM  table 
                ORDER BY id_col DESC LIMIT $start,$max";
    }
  } elseif($flag == "p") {
    if($cat != "") {
      $sel_table="SELECT `order_id_col`, COUNT(`order_id_col`) AS pop, table.* FROM `order`, table 
                WHERE id_col=order_id_col AND category_id=".$cat." 
                GROUP BY `order_id_col` ORDER BY pop DESC LIMIT $start,$max";
    } else {
      $sel_table="SELECT `order_id_col`, COUNT(`order_id_col`) AS pop, table.* FROM `order`, table 
                WHERE id_col=order_id_col GROUP BY `order_id_col` 
                ORDER BY pop DESC LIMIT $start,$max";
    }
  } elseif($flag == "r11") {
    if($cat != "") {
      $sel_table="SELECT feedback.id_col,count(feedback.id_col) AS pop, table.* FROM `feedback`, table 
                WHERE feedback.id_col = table.id_col AND category_id=".$cat." 
                GROUP BY feedback.id_col 
                ORDER BY pop DESC LIMIT $start,$max";
    } else {
      $sel_table="SELECT feedback.id_col,count(feedback.id_col) AS pop, table.* FROM `feedback`, table 
                WHERE feedback.id_col = table.id_col 
                GROUP BY feedback.id_col 
                ORDER BY pop DESC LIMIT $start,$max";
    }
  }

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LVL 11

Assisted Solution

by:level9wizard
level9wizard earned 600 total points
ID: 34197342
Are you trying to have 8 potential separate SELECT statements? Or are you trying to build a single select statement (for example that includes a WHERE statement on category_id and price)?
0
 
LVL 26

Author Comment

by:EddieShipman
ID: 34197614
I just want it refactored so I can understand it, it is a real jumble now.
0
 
LVL 34

Assisted Solution

by:Beverley Portlock
Beverley Portlock earned 600 total points
ID: 34197642
OK - What I have done is to load the code into Eclipse, break the elseif statements into else if statements instead and then hit "reformat source" which promptly turned up several missing quotes and then reformatted the code as shown below.

I think this layout makes it much easier to see what is gong on.

 
<?php


if ($cat != "") {
	$sel_gig = "SELECT * FROM table 
               WHERE category_id=".$cat;
} else
	if ($mny != "") {
		$sel_gig = "SELECT * FROM table 
		               WHERE price=".$mny} else
		if ($flag == "l") {
			if ($cat != "") {
				$sel_gig = "SELECT * FROM table  WHERE category_id=".$cat;
			} else {
				$sel_gig = "SELECT * FROM table";
			}
		} else
			if ($flag == "p") {
				if ($cat != "") {
					$sel_gig = "SELECT * FROM `clientorder`  WHERE category_id=".$cat;
				} else {
					$sel_gig = " SELECT * FROM `clientorder` :";
				}
			} else
				if ($flag == " r11 ") {
					if ($cat != " ") {
						$sel_gig = " SELECT * FROM `feedback` WHERE category_id = ".$cat;
					} else {
						$sel_gig = " SELECT * FROM `feedback`";
					}
				}

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I would then remove brackets around single statements to reduce the clutter further

 
<?php
if ($cat != "")
	$sel_gig = "SELECT * FROM table  WHERE category_id=".$cat;
else
	if ($mny != "")
		$sel_gig = "SELECT * FROM table WHERE price=".$mny;
	else
		if ($flag == "l") {
			if ($cat != "")
				$sel_gig = "SELECT * FROM table  WHERE category_id=".$cat;
			else
				$sel_gig = "SELECT * FROM table";

		} 
          else {
			if ($flag == "p") {
				if ($cat != "")
					$sel_gig = "SELECT * FROM `clientorder`  WHERE category_id=".$cat;
				else
					$sel_gig = " SELECT * FROM `clientorder` :";

			} 
               else
				if ($flag == " r11 ") 
					if ($cat != " ")
						$sel_gig = " SELECT * FROM `feedback` WHERE category_id = ".$cat;
					else
						$sel_gig = " SELECT * FROM `feedback`";

          }

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Now I cab see what's going on. The first statement is

if ( $cat != "")

which means that if you ever get in to the ELSE then $cat == "" so there is no point in testing $cat in the ELSE because you know it is blank.



<?php

if ($cat != "")
	$sel_gig = "SELECT * FROM table  WHERE category_id=".$cat;
else
	if ($mny != "")
		$sel_gig = "SELECT * FROM table WHERE price=".$mny;
	else
		if ($flag == "l") 
			$sel_gig = "SELECT * FROM table";
		else
			if ($flag == "p")
				$sel_gig = " SELECT * FROM `clientorder` :";
			else
				if ($flag == " r11 ")
					$sel_gig = " SELECT * FROM `feedback`";

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0
 
LVL 3

Expert Comment

by:chrios
ID: 34197662
This is equivalent to the code you posted the second time. As you said yourself in your question, the if($cat != "") on lines 10, 19, 29 can never be True because of line 1.


if($cat != "") {
    $sel_table="SELECT * FROM table 
              WHERE category_id=".$cat." 
              LIMIT $start,$max";
} elseif($mny != "") {
    $sel_table="SELECT * FROM  table 
              WHERE table_price=".$mny." 
              LIMIT $start,$max";
} elseif($flag == "l") {
      $sel_table="SELECT * FROM  table 
                ORDER BY id_col DESC LIMIT $start,$max";
} elseif($flag == "p") {
       $sel_table="SELECT `order_id_col`, COUNT(`order_id_col`) AS pop, table.* FROM `order`, table 
                WHERE id_col=order_id_col GROUP BY `order_id_col` 
                ORDER BY pop DESC LIMIT $start,$max";
} elseif($flag == "r11") {
       $sel_table="SELECT feedback.id_col,count(feedback.id_col) AS pop, table.* FROM `feedback`, table 
                WHERE feedback.id_col = table.id_col 
                GROUP BY feedback.id_col 
                ORDER BY pop DESC LIMIT $start,$max";
}

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0
 
LVL 26

Author Comment

by:EddieShipman
ID: 34198240
If you move the first if to an elseif at the end, I think it will work like they intended.
if($mny != "") {
    $sel_table="SELECT * FROM  table 
              WHERE table_price=".$mny." 
              LIMIT $start,$max";
  } elseif($flag == "l") {
    if($cat != "") {
      $sel_table="SELECT * FROM  table 
                WHERE category_id=".$cat." 
                ORDER BY id_col DESC LIMIT $start,$max";
    } else {
      $sel_table="SELECT * FROM  table 
                ORDER BY id_col DESC LIMIT $start,$max";
    }
  } elseif($flag == "p") {
    if($cat != "") {
      $sel_table="SELECT `order_id_col`, COUNT(`order_id_col`) AS pop, table.* FROM `order`, table 
                WHERE id_col=order_id_col AND category_id=".$cat." 
                GROUP BY `order_id_col` ORDER BY pop DESC LIMIT $start,$max";
    } else {
      $sel_table="SELECT `order_id_col`, COUNT(`order_id_col`) AS pop, table.* FROM `order`, table 
                WHERE id_col=order_id_col GROUP BY `order_id_col` 
                ORDER BY pop DESC LIMIT $start,$max";
    }
  } elseif($flag == "r11") {
    if($cat != "") {
      $sel_table="SELECT feedback.id_col,count(feedback.id_col) AS pop, table.* FROM `feedback`, table 
                WHERE feedback.id_col = table.id_col AND category_id=".$cat." 
                GROUP BY feedback.id_col 
                ORDER BY pop DESC LIMIT $start,$max";
    } else {
      $sel_table="SELECT feedback.id_col,count(feedback.id_col) AS pop, table.* FROM `feedback`, table 
                WHERE feedback.id_col = table.id_col 
                GROUP BY feedback.id_col 
                ORDER BY pop DESC LIMIT $start,$max";
    }
  } elseif($cat != "") {
    $sel_table="SELECT * FROM table 
              WHERE category_id=".$cat." 
              LIMIT $start,$max";
  }

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0
 
LVL 3

Accepted Solution

by:
chrios earned 800 total points
ID: 34199079
If you move the first if to an elseif at the end, I think it will work like they intended.
I agree, that makes more sense.
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