ternary operator
条件 ? 结果1 : 结果2 Note: The position in front of the question mark is the condition for judgment. If the condition is met, the result is 1, and if it is not met, the result is 2.
This article compares and explains the ternary operator and if...else... in detail. I hope it will be helpful to everyone.
Today when I was revising my paper online, I came across a sentence that I couldn’t understand:
$if_summary = $row['IF_SUMMARY']==2?'是':'否';Later, Baidu discovered that it was the ternary operator of PHP.
This sentence means that
if($row['IF_SUMMARY']==2){
$if_summary="是";
}else{
$if_summary="否"；
}The function of the ternary operator 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.
Proper use of the ternary operator in PHP programs can make scripts more concise and efficient.
Code format
(expr1) ? (expr2) : (expr3);explain
If condition "expr1" is true, execute statement "expr2", otherwise execute "expr3".
To achieve the same function, if you use conditional process 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.
Such as:
$a>$b ? print "a大于b" : print "a小于b";In fact, the ternary operator can be extended to use. When the set condition is true or not, the execution statement can be more than one sentence. Try the following format:
(expr1) ? (expr2).(expr3) : (expr4).(expr5);We can clearly see that multiple execution statements can be connected using string operators ("."), 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.
Nested use of ternary operators
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 the maintenance of the code in the future. However, compared with process statements such as "if...else", in the above situation, it is indeed too concise, which is its attractiveness.
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 you don't 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 a small unquote manner:
$a>$b ? print "Yes" : "";
$a>$b ? '': print 'No';Note
What should be noted is:
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';
Because one: == should be used to judge equality;
Reason 2: The syntax of the ternary operator is as shown above: (expr1) ? (expr2) : (expr3). Obviously, the above binary and ternary 'wangjinbo' or 'wjb' cannot form a meaningful expression alone;
The correct understanding is:
$_GET['abc'] is a null value (that is, whether (false), ' ', null, 0, undifine in PHP are all equivalent to the Boolean value false). At this time, $str is assigned the value 'wjb', otherwise it is assigned the value 'wangjinbo';
Note:
When there is no condition in the IF statement condition, the content itself $_GET['abc'] is true and the condition is established. The value of str is 'wangjinbo', otherwise the value is 'wjb'; when there is no clear value of true, true means that there is a value, and false means that there is no value.
