PHP basics: Introduction to the usage of while statement in PHP

We introduced the content of the for loop statement in PHP in the previous article . In the next article, we will introduce another loop statement in PHP-the while loop statement. Content.

Let’s first take a brief look at the difference between while loop statements and for loop statements in PHP

If you want to specify the number of loops first, use the for statement

If you want to loop this condition first, use the while statement

Let’s write a while loop statement

The while statement will loop through all matches (true) to the conditional expression and is written in the following format.

初始值; 
while（条件表达式）{ 
执行处理
增加/减少的表达式; 
}

Initial values, conditional expressions and increment/decrement expressions all have this meaning.

Initial value-the first value set

Conditional expression-under what conditions we should perform loop processing

Increase/decrease expression-each processing should How many values ​​to increase or decrease

Let’s look at a specific example

Here weset the variable name to $i

<?PHP basics: Introduction to the usage of while statement in PHP
$i = 0;
while($i < 5){
 echo $i; $i++; 
} 
?>

The running results are as follows:

Finally let’s take a look at Infinite loop

For example, starting from 0, if the conditional expression is not set If so, it will enter an infinite loop by continuously increasing the number with "01234567891011...100...". The execution of this program will never end, and the program will be overloaded and crash.

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