What are the process structures of PHP?

PHP has three process structures: 1. Sequential structure. Each operation in the program is executed top to bottom according to the order in which they are arranged in the source code. 2. The branch structure is used to judge given conditions and then control the flow of the program; the branch structure will judge based on a specific condition and then select one of them for execution. 3. Loop structure refers to a program structure that requires repeated execution of one or more operations in the program until the condition is false or true.

The operating environment of this tutorial: windows7 system, PHP8 version, DELL G3 computer

Process control is a means of controlling the program. If the program is gone For process control, there would be no programming language. Most programs are not controlled by linear execution statements. If the program needs to communicate with the user, the execution sequence must be determined based on user input, and the code may even need to be executed repeatedly. These are all inseparable from process control.

There are three basic program structures in PHP: sequential structure, branch structure, and loop structure.

1. Sequential structure

The sequential structure is the simplest program structure. Each operation in the program is based on their order in the source. The order of arrangement in the code is from top to bottom and executed sequentially.

The flow chart is as follows:

Example:

<?php
//实现$a和$b的值互换
$a=3;
$b=4;
$c=$a;
$a=$b;
$b=$c;
echo&#39;$a=&#39;.$a;
echo"<br/>";
echo&#39;$b=&#39;.$b;
?>

2. Selection structure (branch structure )

The branch structure is also called the conditional structure. It selects the execution path based on clear conditions, rather than strictly following the order. In actual programming, the appropriate one should be selected according to the program flow. A branch statement is a program that changes execution according to the result of a condition.

The flow chart is as follows:

Example:

<?php
$t=date("H");
if ($t>"18") {
echo "晚上好!";
}
?>

3. Loop structure

The loop structure refers to a program structure that requires repeated execution of one or more operations in the program until the condition is false or true.

It determines whether to continue executing a certain function or to exit the loop based on the conditions in the loop body. According to the judgment conditions, the loop structure can be subdivided into the following two forms:

• When type loop structure: judge (condition) first and then execute.

• Until loop structure: execute first and then judge.

The loop structure can be regarded as a combination of a conditional judgment statement and a turnaround statement. In addition, there are three elements of the loop structure: loop variables, loop body and loop termination condition. The loop structure is represented by a judgment box in the program block diagram. The conditions are written in the judgment box. The two exits correspond to the conditions being established and the conditions not being established respectively. Among the different instructions executed at the time, one of them should point to the loop body, and then return from the loop body to the entrance of the judgment box.

The flow chart is as follows:

• "When type" loop: execute block A when the given conditions are met, otherwise block A will not be executed and will jump directly to the following part for execution.

• "Until" loop: Its meaning is: execute block A until the given condition is met (block A will no longer be executed if the condition is met).

provided by php There are three types of loops: while loop, do-while loop, and for loop

Example 1:

<?php
header("Content-type:text/html;charset=utf-8");
$i = 1;
$sum=0;
while($i<=100){
    $sum+=$i;
    $i++;
}
echo "1加到100的值为：".$sum ;
?>

Output result:

1加到100的值为：5050

Example 2: Calculate the sum from 1 to 100

<?php
header("Content-type:text/html;charset=utf-8");
$i = 1;
$sum=0;
do {
        $sum += $i;
        $i++;
    } while ($i <= 100);
echo &#39;1 + 2 + 3 +...+ 99 + 100 = &#39;. $sum;
?>

Output result:

1 + 2 + 3 +...+ 99 + 100 = 5050

Example 3: Find the product of 1 times 100 (factorial of 100)

<?php
$sum=1;
for($i=1; $i<=100; $i++){
    $sum*=$i;
}
echo &#39;1 * 2 * 3 *...* 99 * 100 = &#39;. $sum;
?>

Output:

1 * 2 * 3 *...* 99 * 100 = 9.3326215443944E+157

Recommended learning: "PHP Video Tutorial"

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