Detailed explanation of PHP loop statements while, for, foreach, do while

Detailed explanation of PHP loop statements while, for, foreach, do while_PHP tutorial

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Release： 2016-07-12 09:06:20

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Detailed explanation of PHP loop statements while, for, foreach, do while

1. while loop

while(expression)

{

Loop body; // Repeatedly execute until the expression is false

}

Code:

$index = 1;

while ($index<5)

{

print "Number is {$index} ";

$index ;

}

Run result:

Number is 1

Number is 2

Number is 3

Number is 4

2. do while loop

do {

Loop body;//Repeatedly execute until the expression is false

} while(expression)

Code:

do {

$index ;

print "Number is {$index} ";

} while($index<0);

Run result:

Number is 1

There is a certain difference between the Do While loop statement and while. The difference between them is that do while will be executed first regardless of whether the condition is true, while while will only be executed once if it is true.

3. for loop

There are two types of loops depending on the loop conditions

One: counting loop (usually using for)

Another type: conditional loop (generally use while do-while)

for (expr1; expr2; expr3) {

statement

}

where expr1 is the initial value of the condition. expr2 is the condition for judgment, and logical operators are usually used as the condition for judgment. expr3 is the part to be executed after statement is executed. It is used to change the conditions for the next loop judgment, such as adding one, etc. And statement

is the execution part of the program that meets the conditions. If the program has only one line, the curly brackets {} can be omitted.

The following example is an example of "I won't dare to do it again" written using a for loop. It can be compared with the one using a while loop.

for ($i=1; $i<=10; $i ) {

echo "$i. I won’t dare anymore
";

}

Run result:

1. I won’t dare anymore

2. I won’t dare anymore

3. I won’t dare anymore

4. I won’t dare anymore

5. I won’t dare anymore

6. I won’t dare anymore

7. I won’t dare anymore

8. I won’t dare anymore

9. I won’t dare anymore

10. I won’t dare anymore

4. foreach loop

The foreach statement is used to loop through an array. Each time the loop is executed, the value of the current array element will be assigned to the value variable (the array pointer will move one by one) - and so on

Syntax:

foreach (array as value)

{

code to be executed;

}

Code:

$arr=array("one", "two", "three");

foreach ($arr as $value)

{

echo "Value: " . $value . " ";

}

Run result:

Value: one

Value: two

Value: three

The above are the four loop bodies in PHP. Choose the corresponding loop body to use according to different conditions

Related labels：

statement

source：php.cn

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