[RESOLVED] Some difference in php i don't get from other languages

[Hexxx]

I know php uses the shortcut += and ++, or at least I've seen it used.
But when I try using them in most (all!) of my for loops, they don't have an effect (literlly the values don't change when they're supose to!).

But changing them to their long form works, which I found was strange considering that wouldn't really happen in C++ etc. Are they used differently in PHP?

[Installer]

How about some examples, along with a description of what happens and what you expect to happen with each one?

[Hexxx]

foreach ($temp as $hour => $stations)
{ echo "<br>Hour $hour:<br>";
	$totalMaleCount=0;
	$totalFemaleCount=0;
	foreach ($stations as $station_name => $viewers)  

		{
					$maleCount=0;
					$femaleCount=0;
					foreach ($viewers as $viewer_id) 
					{
							 foreach ($viewers_sex as $k1 => $v1)
							 {
									if ($k1==$viewer_id)
									{
											if ($v1  === 'm')
											{
													$maleCount = $maleCount + 1;
											}
											else
												$femaleCount = $femaleCount + 1;
									}	
							 }
				}
				echo "No. of males for $station_name : ".$maleCount."<br>";	
				$totalMaleCount = $totalMaleCount + $maleCount;
				echo "No. of females for $station_name : ".$femaleCount."<br>";	
				$totalFemaleCount = $totalFemaleCount + $femaleCount;
		}
		echo "Total no. males: " . $totalMaleCount . "<br>";
		echo "Total no. females: " . $totalFemaleCount . "<br>";
}

Instead of $maleCount = $maleCount + 1;
I had $maleCount += 1 and then tried ++$maleCount and they didn't work.
Also I had another snippet

for($c2=0; $c2 < count ($unique_viewers) -1 ; $c2 +=1 )
{
		$query = $query.$unique_viewers[$c2].", ";
}		

I had to put c2 insead of c, I had c used right above in the same code, but thought assigning it over would allow me to use it.

[Installer]

For the first example, "$maleCount += 1" and "++$maleCount" should (will) work. For the second, reassigning "$c" will work. Have you tried putting in some echo statements to see what's going on?

[bradgrafelman]

If you're not convinced they work, try a simple example:

for($c2=0; $c2 < 10 ; $c2 +=1 ) 
{ 
        echo '$c2 is: ' . $c2 . '<br/>';
} 

As Installer pointed out, adding some echo statements within the loop at key places helps debug what's going on inside each iteration... insert some echo statements as in my example code snippet to see values before and after they are (or are not, as it may appear) modified.

[Hexxx]

I know they work, cause they work else where in the code, I just don't know why they didn't work in the nested loops. I tried them with echos and the values were zero.
Well at least now I know that they are suppose to work like i thought they should, at least because you all didn't tell me that they are special in any other way.

[ClarkF1]

Did you try $maleCount++ ?

There is a subtle difference.........more here

[Hexxx]

No I didn't cause I really wanted a pre-increment. I guess I'll use all the long forms for now just to safe.

[Hexxx]

I need some help with this one

foreach ($age_arr1 as $c) 
   foreach ($c as $k => $v )
      {
          foreach ($v as $k1 => $m )
	   // function for m here
       }

I have to go through those lines to modify the value of m. But when I put it in the ampersand, so that I could actually modify the value of m like this

foreach ($age_arr1 as &$c) 
   foreach ($c as $k => &$v ) //line 410
      {
          foreach ($v as $k1 => &$m )
	   // function for m here
       }

I get
Warning: Invalid argument supplied for foreach() in C:\wamp\www\web2\station_ssph.php on line 410

I have used some just like this before and it works, but is not working here when I try to pass by reference.
It works(gives no errors) when I echo($m) without any of the references signs at all.

[bradgrafelman]

Can you do a print_r($age_arr1) for us?

[laserlight]

Typically, to reflect changes in an array looped over with foreach, we would use the key, e.g.

foreach ($array as $key => $value) {
    $array[$key] = $new_value;
}

In your case, using nested foreach loops, this can become rather messy, but it can still be done, e.g.

foreach ($outer_array as $outer_key => $inner_array) {
    foreach ($inner_array as $key => $value) {
        $outer_array[$outer_key][$key] = $new_value;
    }
}

An alternative is to provide functions that do the inner tasks, e.g.

// now we can pass the array by reference
function processInner(&$array, $new_value) {
    foreach ($array as $key => $value) {
        $array[$key] = $new_value;
    }
}

foreach ($outer_array as $outer_key => $inner_array) {
    processInner($outer_array[$outer_key], $new_value);
}

[Hexxx]

here is the print_r, a bit long, but that's what I am working with.

Array
(
    [0] => Array
        (
            [techtv] => Array
                (
                    [0] => 6
                )

    )

[7] => Array
    (
        [techtv] => Array
            (
                [0] => 1
                [1] => 3
            )

    )

[8] => Array
    (
        [techtv] => Array
            (
                [0] => 1
                [2] => 3
            )

    )

[9] => Array
    (
        [techtv] => Array
            (
                [0] => 3
            )

    )

[10] => Array
    (
        [techtv] => Array
            (
                [0] => 3
            )

    )

[11] => Array
    (
        [techtv] => Array
            (
                [0] => 3
            )

    )

[12] => Array
    (
        [techtv] => Array
            (
                [0] => 2
                [1] => 3
            )

    )

[13] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

    )

[14] => Array
    (
        [techtv] => Array
            (
                [0] => 2
                [1] => 4
                [2] => 5
            )

        [NatCore] => Array
            (
                [0] => 8
            )

        [notebook] => Array
            (
                [0] => 6
                [1] => 4
            )

    )

[15] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

        [notebook] => Array
            (
                [0] => 6
            )

    )

[16] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

    )

[17] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

    )

[18] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

    )

[19] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

    )

[20] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

    )

[21] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

    )

[22] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

    )

[23] => 8
)

[Hexxx]

bradgrafelman wrote:

Can you do a print_r($age_arr1) for us?

This it is above. Any idea why it's giving that error?

[Hexxx]

Ok I whole-heartedly belive that PHP, or at least my PHP is cursed. In my post above there, the last element in the array is not supposed to be an 8, although that is what is in the array! I changed a foreach loop for another variable and an 8 happened right there out of nowhere!

With this code the contents of the two print_r are different! (the one with the last value of 8!)

echo '1>>>>>>>>>>>>>>>>>>>'."<br>";
print_r($temp);
echo '1>>>>>>>>>>>>>>>>>>>'."<br>";
for ($c=1; $c < sizeof ($age_groups); $c=$c+1)
{
		echo "";

}

echo '>>>>>>>>>>>>>>>>>>>'."<br>";
print_r($temp);
echo '>>>>>>>>>>>>>>>>>>>'."<br>";

With this code, there are the same (as they should be!) Can someone please tell me why!

echo '1>>>>>>>>>>>>>>>>>>>'."<br>";
print_r($temp);
echo '1>>>>>>>>>>>>>>>>>>>'."<br>";
for ($cz=1; $cz < sizeof ($age_groups); $cz=$cz+1)
{
		echo "";

}

echo '>>>>>>>>>>>>>>>>>>>'."<br>";
print_r ($temp);
echo '>>>>>>>>>>>>>>>>>>>'."<br>";

This is what is there now in both arrays. As it should be.

Array
(
    [0] => Array
        (
            [techtv] => Array
                (
                    [0] => 6
                )

    )

[7] => Array
    (
        [techtv] => Array
            (
                [0] => 1
                [1] => 3
            )

    )

[8] => Array
    (
        [techtv] => Array
            (
                [0] => 1
                [2] => 3
            )

    )

[9] => Array
    (
        [techtv] => Array
            (
                [0] => 3
            )

    )

[10] => Array
    (
        [techtv] => Array
            (
                [0] => 3
            )

    )

[11] => Array
    (
        [techtv] => Array
            (
                [0] => 3
            )

    )

[12] => Array
    (
        [techtv] => Array
            (
                [0] => 2
                [1] => 3
            )

    )

[13] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

    )

[14] => Array
    (
        [techtv] => Array
            (
                [0] => 2
                [1] => 4
                [2] => 5
            )

        [NatCore] => Array
            (
                [0] => 8
            )

        [notebook] => Array
            (
                [0] => 6
                [1] => 4
            )

    )

[15] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

        [notebook] => Array
            (
                [0] => 6
            )

    )

[16] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

    )

[17] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

    )

[18] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

    )

[19] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

    )

[20] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

    )

[21] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

    )

[22] => Array
    (
        [techtv] => Array
            (
                [0] => 2
            )

    )

[23] => Array
    (
        [techtv] => Array
            (
                [0] => 1
            )

    )

)

How did the array get 'corrupted' when I had a $c and back to normal when I put a $cz instead! :mad:

[Hexxx]

laserlight wrote:

In your case, using nested foreach loops, this can become rather messy, but it can still be done, e.g.

foreach ($outer_array as $outer_key => $inner_array) {
    foreach ($inner_array as $key => $value) {
        $outer_array[$outer_key][$key] = $new_value;
    }
}

What does this snippet do? I don't get the purpose of the
foreach ($inner_array as $key => $value)
line as it doesn't seem that it is being used...

[laserlight]

It is being used, in that $key is used.

[sid]

Hexxx wrote:

What does this snippet do? I don't get the purpose of the
foreach ($inner_array as $key => $value)
line as it doesn't seem that it is being used...

the snippet was pretty much the most generic code, hoe you would loop through multi-(in this case 2-)dimensional arrays in php.

as laserlight pointed out, $key gives you the element of the 2nd array level - and it will give you every element of the array $outer_array[$outer_key].

[Hexxx]

Ok I got it now, thanks!

might as well resolve the thread since I guess I would have to abandon the other questions (aka figure it out myself!)