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Detailed explanation of php ternary operator, detailed explanation of operator_PHP tutorial
- WBOYOriginal
- 2016-07-13 09:52:17879browse
Detailed explanation of php ternary operator, detailed explanation of operator
Today when I was revising my paper online, I encountered a statement that I couldn’t understand:
$if_summary = $row[' IF_SUMMARY']==2?'Yes':'No';
Later, Baidu found out that it is PHP's ternary operator
This sentence means the same as
if($row['IF_SUMMARY ']==2){
$if_summary="Yes";
}else{
$if_summary="No";
}
Ternary operator The function is consistent with the "if...else" process statement. It is written in one line, and the code is very concise and the execution efficiency is higher.
Appropriate use of the ternary operator in PHP programs can make scripts more concise and efficient.
The code format is as follows: (expr1) ? (expr2) : (expr3);
Explanation: If the condition "expr1" is true, execute the statement "expr2", otherwise execute "expr3".
To achieve the same function, if you use conditional flow statements, you need to write multiple lines of code:
if(expr1) {
expr2;
} else {
expr3;
}
It can be seen that the goodness of the ternary operator mentioned above is not an exaggeration. However, in most cases we only use the ternary operator when the code is relatively simple, that is, when the execution statement is only a single statement. For example:
$a>$b ? print "a is greater than b" : print "a is less than b";
In fact, the ternary operator can be extended and used. When the set condition is true or not, the execution statement is It can be more than one sentence, try the following format:
(expr1) ? (expr2).(expr3) : (expr4).(expr5);
We can clearly see that multiple execution statements can use strings Operation symbols (".") are connected, and each execution statement is surrounded by small angle brackets to indicate that it is an independent and complete execution statement. After this expansion, its function is closer to the "if...else" process statement.
At the same time, the ternary operator can also be used nested. For example, when a is greater than b: if a is less than c, then x=c-a otherwise x=a-c; otherwise when a is less than b: if b is less than c, then x=c-b otherwise x=b-c:
$a>$ b ? $x=($a<$c ? $c-$a : $a-$c) : $x=($b<$c ? $c-$b : $b-$c);
The readability of the nested ternary operator is not very good, and there may be problems with maintaining the code in the future. However, compared with process statements such as "if...else", in the above situation, it is indeed It's so succinct, and that's the beauty of it.
For those who like to be lazy and pursue code simplicity, using the ternary operator to replace the if process statement should be an excellent choice. Even if there is no need to consider any "element" other than the conditional sentence in the "ternary", using the ternary operator is still more concise than if statements. The following statements are syntactically correct, they omit the second or third "element" in small dequotation marks:
$a>$b ? print "Yes" : "";
$a>$ b ? '': print 'No';
It should be noted that when using the ternary operator, it is recommended to use the print statement instead of the echo statement.
Pay attention to the understanding of the following series of statements:
$str = $_GET['abc'] ? 'wangjinbo' : 'wjb';
This cannot be understood as: When $str is equal to $_GET['abc'], the assigned value is 'wangjinbo' otherwise the assigned value is 'wjb'; reason one: == should be used to judge equality; reason two: the syntax of the ternary operator is as shown above: ( expr1) ? (expr2) : (expr3), obviously the above binary, ternary 'wangjinbo' or 'wjb' cannot form a meaningful expression alone;
The correct understanding is: when $_GET[ When 'abc'] is empty (that is, whether '', null, 0, undifine in PHP are all equivalent to the Boolean value false), assign $str to 'wangjinbo', otherwise assign it to 'wjb';
Original link: bbs.php100.com/read-htm-tid-24239.html