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(PHP 4, PHP 5)
break 结束当前 for,foreach,while,do-while 或者 switch 结构的执行。
break 可以接受一个可选的数字参数来决定跳出几重循环。
<?php
$arr = array( 'one' , 'two' , 'three' , 'four' , 'stop' , 'five' );
while (list (, $val ) = each ( $arr )) {
if ( $val == 'stop' ) {
break;
}
echo " $val <br />\n" ;
}
$i = 0 ;
while (++ $i ) {
switch ( $i ) {
case 5 :
echo "At 5<br />\n" ;
break 1 ;
case 10 :
echo "At 10; quitting<br />\n" ;
break 2 ;
default:
break;
}
}
?>
版本 | 说明 |
---|---|
5.4.0 | break 0; 不再合法。这在之前的版本被解析为 break 1;。 |
5.4.0 | 取消变量作为参数传递(例如 $num = 2; break $num;)。 |
[#1] steve at electricpocket dot com [2012-06-16 12:32:19]
A break statement that is in the outer part of a program (e.g. not in a control loop) will end the script. This caught me out when I mistakenly had a break in an if statement
i.e.
<?php
echo "hello";
if (true) break;
echo " world";
?>
will only show "hello"
[#2] RK [2010-12-17 04:09:46]
If the numerical argument is higher than the number of things which can be broken out of, it seems to me like the execution of the entire program is stopped.
My program had 8 nested loops. Didn't bother counting them, but wrote: break 10. - Result: Code following the loops was not processed.
[#3] Miguel Cruz [2009-04-15 12:37:47]
To make it very clear, if you use "break" with no numerical argument, that's the same as doing "break 1".
"break 0", while allowed, does nothing.
[#4] Anonymous [2008-08-13 21:54:19]
The previous note has a somewhat stupid author: why didn't you put an example?
If I got it right, "case"s in "switch"es always need a "break".
So this switch ...
<?php
switch ( $i ) {
case '1': // Works
echo "$i=1";
break;
case '2': // Works
require( 'include1.inc' );
break;
case '3': // Doesn't work
require( 'include2.inc' );
break;
case '4': // Doesn't work, same reason
require( 'include2.inc' );
default: // Works
echo "$i";
}
?>
... has a problem in case "4" in that it doesn't have a "break" and this file...
include2.inc:
<?php
echo "$i";
break;
?>
... has a problem in that it has a "break" that is not in a "control structure" (like while, for...).
In the same way, although "include2.inc" is "include"d (obvioulsy) in the
<?php ?>
script (of main.php), it still need another
<?php ?>
to wrap its content.
Likewise,
main.php
<?php
echo "<div>This div is generated by php</div>\n";
include 'file.php'; ?>
echo "<div>This div is also generated by php</div>\n";
file.php:
<div>This is an old static HTML div.</div>
... doesn't require "file.php" content to start with "?>" (exit php) and end with "
<?php" (go back to line 3 of main.php). This would FAIL.
!)
(See strange structure ALWAYS fail"?>
Does this really need documentation?
[#5] Anonymous [2008-08-11 11:43:18]
Your break doesn't work because it isn't within a control structure. I use includes that have breaks and they work fine because they are in a control structure (foreach, while, etc.)
[#6] cb [2008-07-08 03:01:38]
Just to note: break doesn't work within included file, results in fatal error.
main.php:
<?php
switch ( $i )
{
case '1': // Works
echo "$i";
break;
case '2': // Works
require( 'include1.inc' );
break;
case '3': // Doesn't work
require( 'include2.inc' );
break;
case '4': // Doesn't work, same reason
require( 'include2.inc' );
default: // Works
echo "$i";
}
?>
include1.inc:
<?php
echo "$i";
?>
include2.inc:
<?php
echo "$i";
break;
?>
I didn't find this documented anywhere.
[#7] alan at synergymx dot com [2008-04-15 12:06:55]
Here is a function that returns specific files in an array, with all of the details. Includes some basic garbage checking.
Variables
$source_folder // the location of your files
$ext // file extension you want to limit to (i.e.: *.txt)
$sec // if you only want files that are at least so old.
$limit // number of files you want to return
The function
function glob_files($source_folder, $ext, $sec, $limit){
if( !is_dir( $source_folder ) ) {
die ( "Invalid directory.\n\n" );
}
$FILES = glob($source_folder."\*.".$ext);
$set_limit = 0;
foreach($FILES as $key => $file) {
if( $set_limit == $limit ) break;
if( filemtime( $file ) > $sec ){
$FILE_LIST[$key]['path'] = substr( $file, 0, ( strrpos( $file, "\\" ) +1 ) );
$FILE_LIST[$key]['name'] = substr( $file, ( strrpos( $file, "\\" ) +1 ) );
$FILE_LIST[$key]['size'] = filesize( $file );
$FILE_LIST[$key]['date'] = date('Y-m-d G:i:s', filemtime( $file ) );
$set_limit++;
}
}
if(!empty($FILE_LIST)){
return $FILE_LIST;
} else {
die( "No files found!\n\n" );
}
}
So....
$source_folder = "c:\temp\my_videos";
$ext = "flv"; // flash video files
$sec = "7200"; // files older than 2 hours
$limit = 2; // Only get 2 files
print_r(glob_files($source_folder, $ext, $sec, $limit));
Would return:
Array
(
[0] => Array
(
[path] => c:\temp\my_videos\
[name] => fluffy_bunnies.flv
[size] => 21160480
[date] => 2007-10-30 16:48:05
)
[1] => Array
(
[path] => c:\temp\my_videos\
[name] => synergymx.com.flv
[size] => 14522744
[date] => 2007-10-25 15:34:45
)
[#8] Gautam [2007-08-22 02:53:40]
<?php
$to_square_root=65536;
$i=1;
$limit=4;
while (true) {
$square_root=sqrt($to_square_root);
echo "Square Root of $to_square_root is $square_root.<BR>";
$to_square_root=$square_root;
$i=$i+1;
if ($i>$limit) // if ($i<$limit) is used, loop breaks on very first execution
break;
}
$loop=$i-1;
echo "This loop is executes for $loop times.";
?>
[#9] pinkgothic at gmail dot com [2007-06-22 04:10:16]
To add to the responses given to "vlad at vlad dot neosurge dot net" - I'd like to note the lack of automatic breaking in 'default' can be a very good thing. Consider this useful snippet:
<?php
switch((string) $_REQUEST['mode']) {
default:
$_REQUEST['mode'] = "search";
// fall through...
case 'search' :
case 'list' :
case 'add' :
case 'edit' :
require(dirname(__FILE__)."/incs/".$_REQUEST['mode'].".php");
break;
}
?>
I personally find that far easier to look at than, for example:
<?php
$valid_modes = array('search','list','add','edit');
if (in_array($_REQUEST['mode'],$valid_modes)) {
require(dirname(__FILE__)."/incs/".$_REQUEST['mode'].".php");
} else {
require(dirname(__FILE__)."/incs/search.php");
}
?>
...and it even has the added benefit that the switch() variant only has one require() statement, which makes for easier maintenance, e.g. if the directory changes, or what-have-you.
(Consider the above pseudocode, please, it's not tested - it's code illustrating a point only.)
[#10] vinyanov at poczta dot onet dot pl [2007-05-05 05:36:14]
Note that the break argument accepts any expression, including a function result. So you may want to dynamically choose the loop level to break from:
<?php
// the print() function returns 1
function icarus()
{
while(print('sea level, '))
while(print('through the clouds, '))
while(print('close the Sun - '))
break rand(print('FEATHERS LOSS! - '), 3);
print('no feathers remaining.');
}
icarus();
?>
[#11] [2007-01-18 06:12:22]
If you wonder how to end execution of a function (as I did), it's that simple: return
function foo($a) {
if(!$a) return;
echo 'true';
// some other code
}
foo(true) will echo 'true', foo(false) won't echo anything (as return ends execution of the function. Of course, therefore there is no need for 'else' before 'echo').
[#12] clean_code at is_good_code dot com [2006-11-08 00:07:07]
"Just an insignificant side not: Like in C/C++, it's not necessary to break out of the default part of a switch statement in PHP."
--Yes it is, it's just that traditionally default: is the last entry of a switch and so nothing happens after.
-If it was, for whatever reason, not the last entry the script would bawk, there is no implicit break; associated with switch.
[#13] traxer at gmx dot net [2005-12-30 06:53:52]
vlad at vlad dot neosurge dot net wrote on 04-Jan-2003 04:21
> Just an insignificant side not: Like in C/C++, it's not
> necessary to break out of the default part of a switch
> statement in PHP.
It's not necessary to break out of any case of a switch statement in PHP, but if you want only one case to be executed, you have do break out of it (even out of the default case).
Consider this:
<?php
$a = 'Apple';
switch ($a) {
default:
echo '$a is not an orange<br>';
case 'Orange':
echo '$a is an orange';
}
?>
This prints (in PHP 5.0.4 on MS-Windows):
$a is not an orange
$a is an orange
Note that the PHP documentation does not state the default part must be the last case statement.
[#14] Ilene Jones [2005-02-21 13:08:02]
For Perl or C programmers...
break is equivelant to last
while(false ! == ($site = $d->read()) ) {
if ($site === 'this') {
break; // in perl this could be last;
}
}