This section provides a tutorial example on how to use 'while' statements to repeat execution of one or more statements while a specified condition is true.
To help us understand how "while" statements work, I wrote the following the tutorial example PHP script:
<?php # WhileStatements.php
# Copyright (c) 2003 by Dr. Herong Yang. http://www.herongyang.com/
#
$upperLimit = 20;
#
print("\n Single-statement \"while\":\n");
$sum = 0; $i = 0;
while ($i<$upperLimit) $sum += ++$i;
print(" Sum of 1 to 20: $sum\n");
#
print("\n Multi-statement \"while\":\n");
$i = 3;
while ($i<$upperLimit) {
$isPrime = true;
$j = 2;
while ($j<$i) {
$isPrime = $i%$j > 0;
if (!$isPrime) break;
$j++;
}
if ($isPrime) print " $i is a prime number.\n";
$i++;
}
#
print("\n Multi-statement \"while ... endwhile\":\n");
$i = 3;
while ($i<$upperLimit):
$isPrime = true;
$j = 2;
while ($j<$i):
$isPrime = $i%$j > 0;
if (!$isPrime) break;
$j++;
endwhile;
if ($isPrime) print " $i is a prime number.\n";
$i++;
endwhile;
?>
If you run this sample script, you should get:
Single-statement "while":
Sum of 1 to 20: 210
Multi-statement "while":
3 is a prime number.
5 is a prime number.
7 is a prime number.
11 is a prime number.
13 is a prime number.
17 is a prime number.
19 is a prime number.
Multi-statement "while ... endwhile":
3 is a prime number.
5 is a prime number.
7 is a prime number.
11 is a prime number.
13 is a prime number.
17 is a prime number.
19 is a prime number.
