SunshinePHP Developer Conference 2015

continue

(PHP 4, PHP 5)

continue は、ループ構造において現在の繰り返しループ の残りの処理をスキップし、条件式を評価した後に 次の繰り返しの最初から実行を続けるために使用されます、

注意: PHP では、continue の動作に関しては switch 文がループ構造とみなされるということに注意しましょう。

continueでは、オプションの引数で 処理をスキップするループ構造のレベルの数を指定できます。 デフォルト値は 1 で、 これは現在のループの終了地点までスキップします。

<?php
while (list($key$value) = each($arr)) {
    if (!(
$key 2)) { // キーが偶数の組をスキップします
        
continue;
    }
    
do_something_odd($value);
}

$i 0;
while (
$i++ < 5) {
    echo 
"Outer<br />\n";
    while (
1) {
        echo 
"Middle<br />\n";
        while (
1) {
            echo 
"Inner<br />\n";
            continue 
3;
        }
        echo 
"This never gets output.<br />\n";
    }
    echo 
"Neither does this.<br />\n";
}
?>

continue の後のセミコロンを省略すると混乱を生じることがあります。 以下の例のようなことをしてはいけません。

<?php
for ($i 0$i 5; ++$i) {
    if (
$i == 2)
        continue
    print 
"$i\n";
}
?>

これは、以下のような結果になることを期待していたのでしょう。

0
1
3
4

しかし、このスクリプトの出力は以下のようになります。

2

continue print "$i\n"; は全体でひとつの式として評価されるので、 print がコールされるのは $i == 2 が true のときだけです (print の返り値が continue への数値引数として渡されます)。

continue の変更履歴
バージョン 説明
5.4.0 continue 0; が使えなくなりました。今までのバージョンでは、これは continue 1; と同じ意味に解釈されていました。
5.4.0 数値引数の部分に変数を渡すこと (例: $num = 2; continue $num;) ができなくなりました。

add a note add a note

User Contributed Notes 17 notes

up
21
jaimthorn at yahoo dot com
4 years ago
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.
up
13
Nikolay Ermolenko
5 years ago
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

*/

?>
up
15
rjsteinert.com
3 years ago
The most basic example that print "13", skipping over 2.

<?php
$arr
= array(1, 2, 3);
foreach(
$arr as $number) {
  if(
$number == 2) {
    continue;
  }
  print
$number;
}
?>
up
5
greg AT laundrymat.tv
9 years ago
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.
up
4
skippychalmers at gmail dot com
3 years ago
To state the obvious, it should be noted, that the optional param defaults to 1 (effectively).
up
3
Geekman
6 years ago
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.
up
6
www.derosetechnologies.com
10 years ago
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.
up
5
Koen
1 year ago
If you use a incrementing value in your loop, be sure to increment it before calling continue; or you might get an infinite loop.
up
1
Anonymous
6 years ago
The continue keyword can skip division by zero:
<?php
$i
= 100;
while (
$i > -100)
{
   
$i--;
    if (
$i == 0)
    {
        continue;
    }
    echo (
200 / $i) . "<br />";
}
?>
up
1
maik penz
2 years ago
Please note that with PHP 5.4 continue 0; will fail with

PHP Fatal error:  'continue' operator accepts only positive numbers

(same is true for break).
up
1
Anonymous
3 years ago
<?php
function print_primes_between($x,$y)
{
    for(
$i=$x;$i<=$y;$i++)
   {
        for(
$j= 2; $j < $i; $j++)  if($i%$j==0) continue 2;
        echo
$i.",";
   }
}
?>

This function, using continue syntax, is to print prime numbers between given numbers, x and y.
For example, print_primes_between(10,20) will output:

11,13,17,19,23,29,
up
1
net_navard at yahoo dot com
8 years ago
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
up
0
tufan dot oezduman at gmail dot com
7 years ago
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.
up
0
dedlfix gives me a hint
9 years ago
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
up
-3
John
7 months ago
<?php

echo"\n";
echo
"\n";

    for (
$i = 0; $i < 5; $i++ ) {

        switch (
$i)
        {

            case
0:
                echo
$i . "b";
                continue;
                echo
$i . "a";
            case
1:   
                echo
$i . "b";
                continue
2;
                echo
$i . "a";
            case
2:   
                echo
$i . "b";
                break;
                echo
$i . "a";
            case
3:
                echo
$i . "b";
                break
2;
                echo
$i . "a";
            case
4:
                echo
$i;
           
        }

        echo
9;

    }

echo
"\n";
echo
"\n";

?>

This results in: 0b91b2b93b

It goes to show that in a switch statement break and continue are the same. But in loops break stops the loop completely and continue just stops executing the current iterations code and moves onto the next loop iteration.
up
-6
szrrya at yahoo dot com
8 years ago
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.
up
-5
Rene
8 years ago
(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.
To Top