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Loops

There are several ways to run a block of statements repeatedly:
   while(cycle condition){statements;}
   do {statements;} while(cycle condition);
   for (pre-loop statements;
         cycle condition;
         cycle statements;){statements;}
   foreach ($array as $value){statements;}
   foreach($array as $key => $value){statements;}
Each of these code segments calculates the sum of 0 to 9.
$a=0; $sum=0;
while ($a<10) $sum+=$a++;

$a=0; $sum=0;
do {$sum+=$a++;} 
while ($a<10);

for ($a=0,$sum=0;$a<10;$a++) $sum+=$a;
foreach is used to loop through the values of an array or class object.
The reference, '&' , allows the values in the array to be changed. Note that the variables retain their last values after the loop.
<!DOCTYPE html>
<html>
<head></head>
<body><?php

$a=[3,4,"foo"=>5,6,100];

foreach($a as $k => &$v) {
   $v*=2;
   echo $k.$v."<br />";
}
echo $k.$v."<br />";
foreach($a as $v2) {
   echo $v2."<br />";
}


?></body>
</html>

06
18
foo10
212
3200
3200
6
8
10
12
200
break [i]; ends the loop instantly. continue [i]; ends the current iteration of loop and starts the next iteration by evaluating the cycle condition. i is an optional integer that tells how many levels of loops to end. If omitted, it will be regarded  as 1, ie. the current level.

RESETRUNFULL
<!DOCTYPE html>
<html>
<head></head>
<body><?php

for ($a=0; $a<5; $a++){  // level 3 for continue
   for ($b=0; $b<5; $b++){  // level 2 for continue
      for ($c=0; $c<5; $c++){  // level 1 for continue
         echo ($a+$b+$c).",";
         if ($a+$b+$c>5) continue 3;
      }
      echo "<br />";
   }
   if ($a>3) break;
}
?></body>
</html>
goto causes the exectution to jump to a point specified by a label, which is a name followed by a ‘:’. It can also be used to run the same statements repeatedly, or get out of multi-level loops.
This calculates the sum of 0 to 9.
RESETRUNFULL
<!DOCTYPE html>
<html>
<head></head>
<body><?php

$i=0; $sum=0;

sectionA:
$sum+=$i++;
if ($i<10) goto sectionA;

echo $sum;

?></body>
</html>