PHP getting started

In PHP, a flow control statement consists of a conditional statement and a loop statement. Among them, the flow control statements include if/else and switch statements, and the loop statements include the while and for statements.

1. IF statement

In PHP, IF statements have two syntax structures. One is to use braces to represent statement blocks, and the other is to use colons to represent statement blocks. The former is generally used in pure code, while the latter is generally used in combination with HTML. The two methods are as follows:

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// Braces indicate statement blocks If ($ value ){ // Operation; } Elseif ($ value ){ // Operation; } Else { // Operation; } // Colon indicates the statement Block If ($ value ): // Operation; Elseif ($ value ): // Operation; Else: // Operation; Endif;

2. switch statement

The switch statement is similar to the C language. It can use numbers and strings as the judgment value. The code it executes starts with the first matching value (or default) and ends with a break. Therefore, do not forget to write break when writing a program. Otherwise, all branches will be executed. The sample code is as follows:

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Switch ($ value ){ Case 'a ': Case 'B ': Echo 'value is a or B .'; Break; Case 'C ': Echo 'value is c .'; Break; Default: Echo 'value is others .'; Break; }

3. while statement

The while statement, like the if statement, also uses two syntax structures. Braces indicate statement blocks and colons indicate statement blocks. The two methods are as follows:

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// Braces indicate statement blocks $ I = 0; While ($ I & lt; 5 ){ Echo $ I; } // Colon indicates the statement Block $ I = 0; While ($ I & lt; 5 ): Echo $ I; Endwhile;

4. do... while statement

The difference between the do... while statement and the while statement is that the while statement is first judged and then executed, while the do... while statement is first executed and then judged. That is to say, even if the condition does not meet the requirements, the do... while statement will be executed once. The statement is as follows:

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$ I = 0; Do { Echo $ I; } While ($ I & lt; 5 );

5. for statement

In the for statement, you should note that it first executes the initialization code, and then runs the judgment statement for each loop. The execution loop then executes the auto-incrementing function. That is to say, if the conditions do not match, the loop will not be executed. There are two syntax structures. Braces indicate statement blocks and colons indicate statement blocks. The two methods are as follows:

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// Braces indicate statement blocks For ($ I = 0; $ I & lt; 5; $ I ++ ){ Echo $ I; } // Colon indicates the statement Block For ($ I = 0; $ I & lt; 5; $ I ++ ): Echo $ I; Endfor;

6. foreach statement

The foreach statement is used to traverse the entire array. Like for, its syntax structure also has two types. Braces indicate statement blocks and colons indicate statement blocks. The two methods are as follows:

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// Braces indicate statement blocks Foreach ($ array as $ value ){ Each $ value; } // Colon indicates the statement Block Foreach ($ array as $ value ): Each $ value; Endforeach;

7. declare statement

A declare statement is a function that is called after N statements are executed. For example

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Register_tick_function ('test '); Declare (ticks = 2 ){ Print '1 '; Print '2 '; Print '3 '; Print '4 '; Print '5 '; } Function test (){ Print 'descare '; }

The result of this code is

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