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continue wird innerhalb von Schleifen verwendet, um den Rest des aktuellen Schleifendurchlaufs abzubrechen und mit der Auswertung der nächsten Bedingung fortzufahren, um dann den nächsten Durchlauf zu beginnen.
Hinweis: Beachten Sie, dass in PHP das switch-Statement im Sinne von continue als Schleifenstruktur betrachtet wird.
continue akzeptiert ein optionales numerisches Argument, das angibt, wie viele Ebenen umschließender Schleifen bis zu ihrem Ende übersprungen werden sollen.
<?php
while (list($key, $value) = each($arr)) {
if (!($key % 2)) { // ignoriere ungerade Werte
continue;
}
mach_etwas_ungerade($value);
}
$i = 0;
while ($i++ < 5) {
echo "Äußere<br />\n";
while (1) {
echo " Mittlere<br />\n";
while (1) {
echo " Innere<br />\n";
continue 3;
}
echo "Das hier wird nie ausgegeben.<br />\n";
}
echo "Das hier ebenfalls nicht.<br />\n";
}
?>
Das Weglassen des Semikolons nach continue kann zu unerwarteten Ergebnissen führen. Hier ist ein Beispiel, das zeigt, was Sie nicht tun sollten.
<?php
for ($i = 0; $i < 5; ++$i) {
if ($i == 2)
continue
print "$i\n";
}
?>
Man könnte meinen, die Ausgabe wäre:
0 1 3 4
aber das Skript gibt in Wirklichkeit ...
2
... aus, da der Rückgabewert des print()-Aufrufs int(1) ist und daher als das oben genannte optionale numerische Argument betrachtet wird.
The remark "in PHP the switch statement is considered a looping structure for the purposes of continue" near the top of this page threw me off, so I experimented a little using the following code to figure out what the exact semantics of continue inside a switch is:
<?php
for( $i = 0; $i < 3; ++ $i )
{
echo ' [', $i, '] ';
switch( $i )
{
case 0: echo 'zero'; break;
case 1: echo 'one' ; XXXX;
case 2: echo 'two' ; break;
}
echo ' <' , $i, '> ';
}
?>
For XXXX I filled in
- continue 1
- continue 2
- break 1
- break 2
and observed the different results. This made me come up with the following one-liner that describes the difference between break and continue:
continue resumes execution just before the closing curly bracket ( } ), and break resumes execution just after the closing curly bracket.
Corollary: since a switch is not (really) a looping structure, resuming execution just before a switch's closing curly bracket has the same effect as using a break statement. In the case of (for, while, do-while) loops, resuming execution just prior their closing curly brackets means that a new iteration is started --which is of course very unlike the behavior of a break statement.
In the one-liner above I ignored the existence of parameters to break/continue, but the one-liner is also valid when parameters are supplied.
Example regarding the condition at the end of the loop and continue:
<?php
$i = 0;
do {
printf('%d ', $i);
continue;
} while( ++$i < 10);
// Output: 0 1 2 3 4 5 6 7 8 9
?>
It gets executed all the time regardless that continue is placed before the while() statement. That does not get skipped.
Using continue and break:
<?php
$stack = array('first', 'second', 'third', 'fourth', 'fifth');
foreach($stack AS $v){
if($v == 'second')continue;
if($v == 'fourth')break;
echo $v.'<br>';
}
/*
first
third
*/
$stack2 = array('one'=>'first', 'two'=>'second', 'three'=>'third', 'four'=>'fourth', 'five'=>'fifth');
foreach($stack2 AS $k=>$v){
if($v == 'second')continue;
if($k == 'three')continue;
if($v == 'fifth')break;
echo $k.' ::: '.$v.'<br>';
}
/*
one ::: first
four ::: fourth
*/
?>
The continue keyword can skip division by zero:
<?php
$i = 100;
while ($i > -100)
{
$i--;
if ($i == 0)
{
continue;
}
echo (200 / $i) . "<br />";
}
?>
For clarification, here are some examples of continue used in a while/do-while loop, showing that it has no effect on the conditional evaluation element.
<?php
// Outputs "1 ".
$i = 0;
while ($i == 0) {
$i++;
echo "$i ";
if ($i == 1) continue;
}
// Outputs "1 2 ".
$i = 0;
do {
$i++;
echo "$i ";
if ($i == 2) continue;
} while ($i == 1);
?>
Both code snippets would behave exactly the same without continue.
a possible explanation for the behavior of continue in included scripts mentioned by greg and dedlfix above may be the following line of the "return" documentation: "If the current script file was include()ed or require()ed, then control is passed back to the calling file."
The example of greg produces an error since page2.php does not contain any loop-operations.
So the only way to give the control back to the loop-operation in page1.php would be a return.
Documentation states:
"continue is used within looping structures to skip the rest of the current loop iteration"
Current functionality treats switch structures as looping in regards to continue. It has the same effect as break.
The following code is an example:
<?php
for ($i1 = 0; $i1 < 2; $i1++) {
// Loop 1.
for ($i2 = 0; $i2 < 2; $i2++) {
// Loop 2.
switch ($i2 % 2) {
case 0:
continue;
break;
}
print '[' . $i2 . ']<br>';
}
print $i1 . '<br>';
}
?>
This outputs the following:
[0]
[1]
0
[0]
[1]
1
Switch is documented as a block of if...elseif... statements, so you might expect the following output:
[1]
0
[1]
1
This output requires you to either change the switch to an if or use the numerical argument and treat the switch as one loop.
(only) the reason that is given on the "Continue with missing semikolon" example is wrong.
the script will output "2" because the missing semikolon causes that the "print"-call is executed only if the "if" statement is true. It has nothing to to with "what" the "print"-call would return or not return, but the returning value can cause to skip to the end of higher level Loops if any call is used that will return a bigger number than 1.
<?php
continue print "$i\n";
?>
because of the optional argument, the script will not run into a "unexpected T_PRINT" error. It will not run into an error, too, if the call after continue does return anything but a number.
i suggest to change it from:
because the return value of the print() call is int(1), and it will look like the optional numeric argument mentioned above.
to
because the print() call will look like the optional numeric argument mentioned above.
Hello firends
It is said in manually:
continue also accepts an optional numeric argument which tells it how many levels of enclosing loops it should .
In order to understand better this,An example for that:
<?php
/*continue also accepts an optional numeric argument which
tells it how many levels of enclosing loops it should skip.*/
for($k=0;$k<2;$k++)
{//First loop
for($j=0;$j<2;$j++)
{//Second loop
for($i=0;$i<4;$i++)
{//Third loop
if($i>2)
continue 2;// If $i >2 ,Then it skips to the Second loop(level 2),And starts the next step,
echo "$i\n";
}
}
}
?>
Merry's christmas :)
With regards,Hossein
a possible solution for
greg AT laundrymat.tv
I've got the same problem as Greg
and now it works very fine by using
return() instead of continue.
It seems, that you have to use return()
if you have a file included and
you want to continue with the next loop
You using continue in a file included in a loop will produce an error. For example:
//page1.php
for($x=0;$x<10;$x++)
{
include('page2.php');
}
//page2.php
if($x==5)
continue;
else
print $x;
it should print
"012346789" no five, but it produces an error:
Cannot break/continue 1 level in etc.
In the same way that one can append a number to the end of a break statement to indicate the "loop" level upon which one wishes to 'break' , one can append a number to the end of a 'continue' statement to acheive the same goal. Here's a quick example:
<?
for ($i = 0;$i<3;$i++) {
echo "Start Of I loop\n";
for ($j=0;;$j++) {
if ($j >= 2) continue 2; // This "continue" applies to the "$i" loop
echo "I : $i J : $j"."\n";
}
echo "End\n";
}
?>
The output here is:
Start Of I loop
I : 0 J : 0
I : 0 J : 1
Start Of I loop
I : 1 J : 0
I : 1 J : 1
Start Of I loop
I : 2 J : 0
I : 2 J : 1
For more information, see the php manual's entry for the 'break' statement.
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