PHP: Hypertext Preprocessor

continue

(PHP 4, PHP 5, PHP 7, PHP 8)

L'instruction continue est utilisée dans une boucle afin d'éluder les instructions de l'itération courante et de continuer l'exécution à la condition de l'évaluation et donc, de commencer la prochaine itération.

Note: En PHP, la structure switch est considérée comme une boucle par continue. continue se comporte comme break (lorsque aucun argument n'est passé) mais émettra un avertissement, car il est probable que ceci soit une erreur. Si un switch se trouve à l'intérieur d'une boucle, continue 2 va continuer sur la prochaine itération de la boucle externe.

continue accepte un argument numérique optionnel qui vous indiquera combien de structures emboîtées doivent être éludées. La valeur par défaut est 1, ce qui revient à aller directement à la fin de la boucle courante.

<?php
$arr = ['zero', 'one', 'two', 'three', 'four', 'five', 'six'];
foreach ($arr as $key => $value) {
    if (0 === ($key % 2)) { // évite les membres pairs
        continue;
    }
    echo $value . "\n";
}
?>

Les exemples ci-dessus vont afficher :

one
three
five

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

Les exemples ci-dessus vont afficher :

Outer
Middle
Inner
Outer
Middle
Inner
Outer
Middle
Inner
Outer
Middle
Inner
Outer
Middle
Inner

Oublier le point virgule après continue peut porter à confusion. Voici un exemple de ce que vous ne devez pas faire :

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

On peut s'attendre à ce que le résultat soit :

**Historique pour `continue`**
Version	Description
7.3.0	`continue` à l'intérieur d'un `switch` qui tente d'agir comme une déclaration `break` pour `switch` émettra `E_WARNING`.

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User Contributed Notes 7 notes

down

140

jaimthorn at yahoo dot com ¶

14 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.

down

Nikolay Ermolenko ¶

15 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



*/



?>

down

Koen ¶

11 years 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.

down

rjsteinert.com ¶

13 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;
}
?>

down

www.derosetechnologies.com ¶

20 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.

down

Geekman ¶

16 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.

down

tufan dot oezduman at gmail dot com ¶

17 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.

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