Examples introduce the four loops of while, do...while, for, and foreach

#while loop in php, loops to execute the code block a specified number of times, or loops to execute the code block when the specified condition is true.
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When we write code, we often need to repeat a block of code multiple times. We can use the while loop statement to complete this task.

while--As long as the specified condition is true, the code block will be executed in a loop.

do...while--First execute the code block once, and then repeat the loop when the specified condition is true.
for--The number of times the loop executes the code block.

foreach
--Loop the code block based on each element in the array.

while loopThe while statement loops through the code block until the specified condition is not true.

while(condition)

{

Code to be executed in a loop;
}

Case: Set the value of a variable a to 11 ($a=11).

Then, as long as a
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$a=11;
while($a<=20){
 echo "输出数值：".$a."";
 $a++;
}

will output the following results: while output value: 11

while output value: 12

while output value: 13

while output value: 14
while output value: 15
while output value: 16
while output value: 17
while output value: 18
while output value: 19
while output value: 20

The following is the example code:

<?php
$a=11;
while($a<=20){
 echo "while输出数值：".$a."<br>";
 $a++;
}
?>
while循环Code、

do...while loop do...The while statement will execute the code at least once, then check the condition, and the loop will repeat.

Syntax

do

{

Code to be executed;
}
while(condition)

Example

The following example first sets the value of variable a to 1 ($a=11). Then, start the do...while loop. The loop increments the value of variable a by 1 and then outputs it. First check the condition (a is light rain or equal to 20). As long as a is less than or equal to 5, the loop will be executed accordingly:

do...while output value: 11

do...while output Value: 12

do...while Output value: 13
do...while Output value: 14
do...while Output value: 15
do...while Output value: 16
do...while output value: 17
do...while output value: 18
do...while output value: 19
do...while output value: 20

The following is an example code:

<?php
$a=11;
do{
 echo"do...while输出数值：".$a."<br/>";
 $a++;
}while($a<=20);
?>
do...while循环代码

for loopLoop to execute the code block the specified number of times , or loop through a block of code when a specified condition is true.

The for loop is used when you know in advance the number of times the script needs to run.

Syntax

for(initial value; conditional increment; ){

Code to be executed

}

Initial value: Mainly initializes a variable value to set a counter (but it can be any code that is executed once at the beginning of the loop).

Conditions: Restrictions on loop execution. If TRUE, the loop continues. If FALSE, the loop ends.

Increment: Mainly used to increment the counter (but can be any code that is executed at the end of the loop).

Note: The above initial value and increment parameters can be empty, or have multiple

expressions

(separated by commas).

Example

for output value: 11

for output value: 12

for output value: 13
for output value: 14
for output value: 15
for output value: 16
for output value: 17
for output value: 18
for output value: 19
for output value: 20

The following is the example code:

<?php
 for($a=11;,$a<=20;,$a++){
  echo "for输出数值：".$a."<br/>";
 }
 ?>

foreach loopthe foreach loop is used to

traverse the array

. Syntax

foreach ($array as $value){

To execute the code;
}

Every time the loop is performed, the value of the current array will be assigned to $ value variable (the array pointer will move one by one), and on the next loop, you will see the next value in the array.

Example

The following

example demonstrates

a loop that outputs the values ​​of a given array: Outputs the array values ​​one by one ：one

Output the array values ​​one by one: two

Output the array values ​​one by one: three
Output the array values ​​one by one: four
Output the array values ​​one by one: five

The following is an example Code:

<?php
 $x=array("one","two","three","four","five");
 foreach($x as $value){
  echo "逐一输出数组值：".$value."<br/>";
 }
 ?>

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