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while

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

while-Schleifen sind der einfachste Typ von Schleifen in PHP. Sie verhalten sich wie ihre Pendants in C. Die Grundform einer while-Schleife ist:

while (bedingung)
    anweisung

Die Bedeutung einer while-Schleife ist simpel. Die Schleife weist PHP an, die untergeordnete(n) Anweisung(en) wiederholt auszuführen, solange die while-Bedingung zutrifft. Die Bedingung wird jedes Mal am Anfang der Schleife überprüft, Das bedeutet, dass die Ausführung der untergeordneten Anweisungen nicht stoppt, auch wenn sich der Wahrheitsgehalt der Bedingung zwischendurch ändert (jedes Mal, wenn PHP die Anweisungen ausführt, handelt es sich um eine Runde). Wenn die while-Bedingung von Anfang an nicht zutrifft, werden die untergeordneten Anweisung nicht ein einziges Mal ausgeführt.

Wie bei if-Abfragen können mehrere Statements innerhalb der selben Schleife mit geschleiften Klammern oder mithilfe der alternativen Syntax gruppiert werden:

while (bedingung):
    anweisung
    ...
endwhile;

Die folgenden Beispiele sind identisch und geben die Zahlen von 1 bis 10 aus:

<?php
/* Beispiel 1 */

$i 1;
while (
$i <= 10) {
    echo 
$i++;  /* der ausgegebene Wert ist $i bevor
                   er erhöht wird (post-increment) */
}

/* Beispiel 2 */

$i 1;
while (
$i <= 10):
    echo 
$i;
    
$i++;
endwhile;
?>

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User Contributed Notes 9 notes

up
2
Dan Liebner
26 days ago
While loops don't require a code block (statement).

<?php

while( ++$i < 10 ); // look ma, no brackets!

echo $i; // 10

?>
up
-23
scott at mstech dot com
11 years ago
Just a note about using the continue statement to forego the remainder of a loop - be SURE you're not issuing the continue statement from within a SWITCH case - doing so will not continue the while loop, but rather the switch statement itself.

While that may seem obvious to some, it took a little bit of testing for me, so hopefully this helps someone else.
up
-8
mparsa1372 at gmail dot com
1 month ago
The example below displays the numbers from 1 to 5:

<?php
$x
= 1;

while(
$x <= 5) {
  echo
"The number is: $x <br>";
 
$x++;
}
?>

This example counts to 100 by tens:

<?php
$x
= 0;

while(
$x <= 100) {
  echo
"The number is: $x <br>";
 
$x+=10;
}
?>
up
-34
ravenswd at gmail dot com
11 years ago
I find it often clearer to set a simple flag ($finished) to false at the start of the loop, and have the program set it to true when it's finished doing whatever it's trying to do. Then the code is more self-documenting: WHILE NOT FINISHED keep going through the loop. FINISHED EQUALS TRUE when you're done. Here's an example. This is the code I use to generate a random filename and ensure that there is not already an existing file with the same name. I've added very verbose comments to it to make it clear how it works:

<?php
$finaldir
= 'download';

$finished = false;                       // we're not finished yet (we just started)
while ( ! $finished ):                   // while not finished
 
$rn = rand();                          // random number
 
$outfile = $finaldir.'/'.$rn.'.gif';   // output file name
 
if ( ! file_exists($outfile) ):        // if file DOES NOT exist...
   
$finished = true;                    // ...we are finished
 
endif;
endwhile;                               
// (if not finished, re-start WHILE loop)
?>
up
-44
chayes at antenna dot nl
19 years ago
At the end of the while (list / each) loop the array pointer will be at the end.
This means the second while loop on that array will be skipped!

You can put the array pointer back with the reset($myArray) function.

example:

<?php
$myArray
=array('aa','bb','cc','dd');
while (list (
$key, $val) = each ($myArray) ) echo $val;
reset($myArray);
while (list (
$key, $val) = each ($myArray) ) echo $val;
?>
up
-41
synnus at gmail dot com
5 years ago
<?php

// test While Vs For php 5.6.17

$t1 = microtime(true);
$a=0;
while(
$a++ <= 1000000000);
$t2 = microtime(true);
$x1 = $t2 - $t1;
echo
PHP_EOL,' > while($a++ <= 100000000); : ' ,$x1, 's', PHP_EOL;

$t3 = microtime(true);
for(
$a=0;$a <= 1000000000;$a++);
$t4 = microtime(true);
$x2 = $t4 - $t3;
echo
PHP_EOL,'> for($a=0;$a <= 100000000;$a++); : ' ,$x2, 's', PHP_EOL;

$t5 = microtime(true);
$a=0; for(;$a++ <= 1000000000;);
$t6 = microtime(true);
$x3 = $t6 - $t5;
echo
PHP_EOL,' > $a=0; for(;$a++ <= 100000000;); : ' , $x3, 's', PHP_EOL;

//> while($a++ <= 100000000);   = 18.509671926498s
//
//> for($a=0;$a <= 100000000;$a++);  =  25.450572013855s
//
//> $a=0; for(;$a++ <= 100000000;);  =  22.614907979965s

// ===================

//> while($a++ != 100000000); : 18.204656839371s
//
//> for($a=0;$a != 100000000;$a++); : 25.025605201721s
//
//> $a=0; for(;$a++ != 100000000;); : 22.340576887131s

// ===================

//> while($a++ < 100000000); : 18.383454084396s
//
//> for($a=0;$a < 100000000;$a++); : 25.290743112564s
//
//> $a=0; for(;$a++ < 100000000;); : 23.28609919548s

?>
up
-40
nickleus at gmail dot com
3 years ago
<?php
$i
= -1;
while (
$i) {
    echo
$i++;
}
?>
outputs  "-1" then stops because "0" (zero) gets evaluated as FALSE.

this demonstrates why it's important for a PDO statement fetch-ing a column value inside a while-loop to test explicitly for FALSE.
up
-43
qeremy [atta] gmail [dotta] com
8 years ago
Instead of this usage;

<?php
$arr
= array("orange", "banana", "apple", "raspberry");

$i = 0;
while (
$i < count($arr)) {
  
$a = $arr[$i];
   echo
$a ."\n";
  
$i++;
}
// or
$i = 0;
$c = count($arr);
while (
$i < $c) {
  
$a = $arr[$i];
   echo
$a ."\n";
  
$i++;
}
?>

This could be more efficient;

<?php
while ($a = $arr[1 * $i++]) echo $a ."\n";
?>
up
-51
er dot sarimkhan786 at gmail dot com
5 years ago
simple pyramid pattern program using while loop
<?php
$i
=1;
while(
$i<=5)
{
   
$j=1;
    while(
$j<=$i)
    {
      echo
"*&nbsp&nbsp";
     
$j++;     
    }
    echo
"<br>";
   
$i++;
}
?>
// or alternatively you can use:
<?php
$i
=1;
while(
$i<=5):

   
$j=1;
    while(
$j<=$i):
      echo
"*&nbsp&nbsp";
     
$j++;     
    endwhile;
   
    echo
"<br>";
   
$i++;
endwhile;
?>
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