Introduction to the use of switch statements in PHP _php tutorial

This article describes in detail the use of the switch statement in PHP, as well as the switch case in the condition of 0 o'clock processing method, there is a need to understand the students can refer to.

Switch statement
If you want to selectively execute one of several blocks of code, use the Switch statement.

Use the Switch statement to avoid lengthy if. ElseIf. else code block.

Grammar

The code is as follows	Copy Code
switch (expression) { Case Label1: Code to is executed if expression = Label1; Break Case LABEL2: Code to is executed if expression = Label2; Break Default Code to be executed If expression is different From both Label1 and Label2; }

Instance
Working principle:

Perform a single calculation on an expression (usually a variable)
Compare the value of an expression with the value of a case in the structure
If there is a match, the code associated with the case is executed
After the code executes, the break statement prevents the code from jumping into the next case to continue execution
If no case is true, use the default statement

The code is as follows	Copy Code
Switch ($cps _sign) { Case ' Yiqifa ': Case ' Chengguo ': Case ' Roiyiqifa ': Case ' LKT ': Case ' Fanli ': Case ' Qqfanli ': Case ' Weiyi ': Case ' Yoyi ': $sql = "INSERT into sa_cps_list (' UV ', ' s_time ', ' cps ', ' url ') VALUES (' {$uv} ', {$timestamp}, ' {$cps _sign} ', ' {$url} ')"; echo $sql; exit (); mysql_query ($sql); Break Default Break }

Have a closer look at the procedure, is it a switch and case trouble? So, write demo test.
The output is: BOOL (TRUE) bool (false) XXX

The code is as follows	Copy Code
Var_dump ("==0"); Var_dump ("===0"); $errid = "; Switch ($errid) { Case 0: echo "XXX"; Break Default echo "YYY"; }

The truth, the original switch/case structure, compare case value is = = instead of = = =. Thus, the emptiness is equal to 0, and the result I receive is of course the wrong one.
No way, the program does not want to change, after all, many conditions when the switch/case than a bunch of if let people look comfortable. Find a way to do it. Oh.

The code is as follows	Copy Code
$result = "; if (Is_numeric ($err _id) = = = False) { $result. = ' outage or timeout, no return value '; return $result; } Switch ($err _id) { Case XXX: .......... }

Problem solved, first determine whether the return value is a value, if not a value, direct return.
You must be careful when writing switch/case to judge numbers, especially when there are 0 of these prodigal values.

Comparison of switch statements and ElseIf statements
In a switch statement, the condition is only one time, and then compared to each case, and in the ElseIf statement, the condition is evaluated again. If your condition is more complex, or multiple loops, using a switch statement will be faster

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