[SOLVED] Find out when a variable's value has changed

[joshgarrod]

I have a loop that prints a list of information, I want it to do something different if the value of a certain variable changes? Thanks

[Maq]

Temporarily store it, if it doesn't equal the temp var, then do something.

[joshgarrod]

can you show me an example please, I am not sure how to structure it. Thank you for your time

[byte1918]

can you show me an example please, I am not sure how to structure it. Thank you for your time

 

$temp_variable = $variable

#code goes here...

if ($variable != $temp_variable){

      #variable has changed;}

else{

    #variable is the same;

}

[joshgarrod]

But with a loop it won't work as it resets the variable back every time around, or is there a way to prevent this?

[taquitosensei]

something along these lines

at the end of your loop set $oldvariable

$variable=3; 
for($a=0;$a<=20;$a++)
{
$variable=$a; 
if($variable!=$oldvariable) { 
// do whatever here 
}
$oldvariable=$variable; 
}

[joshgarrod]

but when you compare $variable and $oldvariable, you haven't actually set $oldvariable, sorry this ois really confusing me...

[PFMaBiSmAd]

If you show the loop you are currently using, someone can directly show you the implementation that would be used with that loop.

 

But in general, you initialize the $old variable before the loop to a value it will never see as data, such as an empty string ''. Then you test if the value is not equal to the $old variable. If the values are not equal, you do the sepcial processing AND you set the $old variable equal to the variable you at testing so that you will detect the next change in the value.

[joshgarrod]

Ok here is my code, thanks:

 

<?php

mysql_connect("host", "user", "pass") or die(mysql_error()); 
mysql_select_db("quest") or die(mysql_error()); 

$query = ("SELECT * FROM directory ORDER BY category ASC");
$result = mysql_query($query)
or die ('Error in query: $query. ' . mysql_error());

while($row = mysql_fetch_object($result)) 
{

$ref = $row->ref;
$category = $row->category;
$count = 120;
$company = $row->company;
$descr = $row->descr;
$descrshort = substr($descr,0,$count); //limiting the amount of characters set by var count
$web = $row->web;
$tel = $row->tel;
$road = $row->road;
$town = $row->town;
$county = $row->county;
$temp_category = $category;

if ($category != $temp_category){
      #variable has changed;}
 echo "<h1>$category</h1>";
 }
else {
     #variable is the same;
 echo "<div id=\"show_row\"><h1>$company</h1><strong>Location: </strong>$town, $county<br /><br />$descrshort ...<a href=\"view_company_details.php?ref=$ref\">More>></a></div>";
 $temp_category = $category;
}

}

?>

[PFMaBiSmAd]

you initialize the $old variable before the loop to a value it will never see as data, such as an empty string ''. Then you test if the value is not equal to the $old variable. If the values are not equal, you do the sepcial processing AND you set the $old variable equal to the variable you at testing so that you will detect the next change in the value.

 

$temp_category = '';
while($row = mysql_fetch_object($result)) 
{

....

if ($category != $temp_category){
      #variable has changed;}
    echo "<h1>$category</h1>";
    $temp_category = $category;
    }
else {
     #variable is the same;
    echo "<div id=\"show_row\"><h1>$company</h1><strong>Location: </strong>$town, $county<br /><br />$descrshort ...<a href=\"view_company_details.php?ref=$ref\">More>></a></div>";
}
}

 

[joshgarrod]

How do I get the information to set the variable $temp_category before the loop?

[joshgarrod]

Ok, sorry I get it. Set the variable before the loop with no value. I will try it.

[joshgarrod]

Worked, thanks for your help guys