note 50072 deleted from control-structures.while by philip
| From: | philip@php.net | Date: | Thu, 27 Apr 2006 15:53:36 +0000 |
| Subject: | note 50072 deleted from control-structures.while by philip | ||
| References: | 1 | Groups: | php.notes |
| Request: | Send a blank email to php-notes+get-109865@lists.php.net to get a copy of this message | ||
Note Submitter: mortoray at ecircle-ag dot com
----
Note that while loops (and likely for, if's, and otherwise) do not introduce a new variable
locality, that is, variables introduced in the loop will exist outside the loop and/or retain their
value on further iterations of the loop.
while( true ) {
$val = 15;
break;
}
print( "$val" ); //prints 15
This can introduce an insidious bug if you are using references. By Example:
$i = 0;
$set = array();
while( $i < 5 ) {
$item = $i;
$set[] =& $item;
$i++;
}
print_r( $set );
Every item in the array has a value of 4, probably not what you were expecting/wanting. To do what
you expect add a unset statement like this:
$i = 0;
$set = array();
while( $i < 5 ) {
unset( $item );
$item = $i;
$set[] =& $item;
$i++;
}
print_r( $set );
Obviously for integers you wouldn't use refereneces, but if you are using classes or arrays
this problem comes up.