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Php for loop with 2 variables?

Posted by: admin April 23, 2020 Leave a comment

Questions:

is it possible to do this? (here is my code)

for ($i = 0 ; $i <= 10 ; $i++){
  for ($j = 10 ; $j >= 0 ; $j--){
     echo "Var " . $i . " is " . $k . "<br>";
  }
}

I want something like this:

var 0 is 10

var 1 is 9

var 2 is 8 …

But my code is wrong, it gives a huge list. Php guru, help me !!

How to&Answers:

Try this:

for ($i=0, $k=10; $i<=10 ; $i++, $k--) {
    echo "Var " . $i . " is " . $k . "<br>";
}

The two variables $i and $k are initialized with 0 and 10 respectively. At the end of each each loop $i will be incremented by one ($i++) and $k decremented by one ($k--). So $i will have the values 0, 1, …, 10 and $k the values 10, 9, …, 0.

Answer:

You could also add a condition for the second variable

for ($i=0, $k=10; $i<=10, $k>=0 ; $i++, $k--) {
    echo "Var " . $i . " is " . $k . "<br>";
}

Answer:

You shouldn’t be using two for-loops for what you’d like to achieve as you’re looping 121 times total (11×11). What you really want is just to have a counter declared outside of the loop that tracks j, and then decrement j inside the loop.

Edit: Thanks Gumbo for catching the inclusion for me.

Answer:

If, as your code looks like, you have two values running the opposite direction you could simply substract:

echo "Var " . $i . " is " . 10 - $i . "<br>";

But I guess that’s not really what you want? Also, be careful with the suggested comma operator. While it is a nice thing it can cause naughty side effects in other languages like C and C++ as PHP implements it differently.

Answer:

To expand on the other (correct) answers, what you were doing is called nesting loops. This means that for every iteration of the outer loop (the first one), you were completing the entire inner loop. This means that instead of 11 outputs, you get 11 + 11 + 11 + ... = 11 * 11 outputs

Answer:

array_map(function($i) {
    echo "Var {$i} is ".(10-$i)."<br/>".PHP_EOL; 
}, range(1,10));

Answer:

I tried to get a start and end time and store in the database, given a start and end time, you loop through each time using two variables i&j

   $start = "09:00";
   $end = "18:00";
   $strEnTim = strtotime("10.00");

   $slotStart = strtotime($start);
   $slotEnd = strtotime($end);
   $slotNow = $slotStart;

   for( $i=$slotStart, $j=$strEnTim; $i, $j<=$slotEnd; $i+=3600,  $j+=3600) 
   {
        if(( $i < $slotNow) && ( $j < $strEnTim)) continue;
        Slot::create([
            'start_time' => date("H:i",$i),
            'end_time' => date("H:i", $j)
        ]);
   }