If statements and while loops, back to basics!

trufla

I realised that as a newbie I had decided to run before I could walk! This is bad bad bad for my understanding!

I have gone back to learn the basics of statements and while loops and carrying out variable exercises, just testing out crude examples and trying to make the logic stick!

I have an incredibly base question: I have some code:

<?php
$am = "am";
$pm = "pm";

// for ($hour > 5; $hour <=21){
// print "<br>"; 
// }

$hour = 6;

while ($hour <= 11){
print "<br> ". $hour.$am;
++$hour;
}

if ($hour > 11){
print "<br>".$hour.$pm;
}

while ($hour > 11){
print"<br> ". $hour.$pm;
++$hour;
}


?>

The premise is that I want to print out the number 6-21. 6-11 must be appended to am. numbers 12-21 must be appended to pm. (24hour clock thingy!).

My code is printing infinately, so I need to break the loop when $hour is incremented to 21.

I have a vague undestanding of for loops (like the commented out bit of the code) but I am not sure how to intergrate it with the rest of the code.

I am also aware that there are probably more elegant ways of doing this.

Any pointers or feedback greatly appreciated!

Trufla the noob!

mattvenables

Your code working with a while loop (the main problem was the line ++$hour;... it shoudl be $hour++😉

<?php
$am = "am";
$pm = "pm";

$hour = 6;

while ($hour <= 11){
print "<br> ". $hour.$am;
$hour++;
}

while ($hour > 11){
  print"<br> ". $hour.$pm;
  $hour++;
}

?>

Your code working with the for loop (note that it has THREE arguments: one to set the variable, one to check it to a clause, and one to increment it):

<?php
$am = "am";
$pm = "pm";


for ($hour =6; $hour <=21; $hour++){
  print "<br>" . $hour; 
  if($hour<=11) { print $am;
  } else { print $pm;
   }
 }

?>

laserlight

Sometimes you just need to think clearly.

<?php
//The premise is that I want to print out the number 6-21.
for ($i = 6; $i <= 21; $i++) {
	if ($i <= 11) {
		//6-11 must be appended to am
		echo $i . 'am';
	} else {
		//numbers 12-21 must be appended to pm
		echo $i . 'pm';
	}
}
?>

trufla

Cheers guys!

I think the main problem I have is that if I cannot see it straight away, I get frightened away from mentally persisting!🙁

I NEED TO GET OVER THIS....

and....🆒....relax, and work smarter!

drawmack

also your second while loop should say while $hour < 22 not $hour > 11 cause $hour is always greater then 11 at this point. I'll demonstrate:

<?php
$am = 'am';
$pm = 'pm';

$hour = 6;
echo 'Starting First Loop<blockquote>';
//I use < 12 cause it's easier on the cpu then <= 11
//and they mean the same thing when you're working
//with integers. The only time you should use <= is when
//you're dealing with floats.
while($hour < 12) {
    echo $hour . ' ' . $am . '<br />';
    $hour++;
}
echo '</blockquote>';

/*this prints
    6 am
    7 am
    8 am
    9 am
    10 am
    11 am

note that $hour is 12 after exiting this loop because 
when it's 11 the loop executes which increments
$hour to 12 and then the loop exits. The next line 
of code is provided as proof of this.
*/
echo '<br />Between Loops: ' . $hour . ' ' . $pm . '<br /><br />';

echo 'Starting Second Loop<blockquote>';
//see explaination of first while loop for why I use 22 here. 
while($hour < 22) {
    echo $hour . ' ' . $pm . '<br />';
    $hour++;
}
echo '</blockquote>';

/* this prints
    12 pm
    13 pm
    14 pm
    15 pm
    16 pm
    17 pm
    18 pm
    19 pm
    20 pm
    21 pm

note that $hour is 22 after exiting this loop because 
when it's 21 the loop executes which increments 
$hour to 22 and then the loop exits. The next line
of code is provided as proof of this.
*/
echo '<br />After Second Loop: ' . $hour . ' ' . $pm . '<br /><br />';
?>

As with most example code this is very verbose and a very round about way of doing this. In a productions system this code would most likely be implemented with a for loop and loook something like this:

<?
$meridian = array('am','pm');
//for loop goes from 5 to 21 to account for modulous arithmetic used later
for($i=5;$i<21;$i++) {
    //$i%12 is the remainder from $i/12
    //intval of ($i+1)/12 always rounds down.
    echo (($i%12)+1) . ' ' . $meridian[intval(($i+1)/12)] . '<br />'; 
} //end for
?>

You probably won't understand this second code snippet right now. However, you should be able to grasp the first one and understanding why the second one works should be a goal to work towards.