Summary of knowledge points about PHP ternary operator

Ternary operator syntax: condition ? result 1 : result 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. Let’s discuss this in detail below.

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 on Baidu, I found out that it was PHP’s ternary operation. The meaning of the symbol

is equivalent to the function of

if($row['IF_SUMMARY']==2){ $if_summary="是"; }else{ $if_summary="否"； }

The function of the ternary operator and the "if...else" process statement Consistent, it is written in one line, 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 process statements, you need to write multiple lines of code:

if(expr1) { expr2; } else { expr3; }

It can be seen that the previous It is not an exaggeration to say that the ternary operator is good. 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 sentence. For example:

$a>$b ? print "a大于b" : print "a小于b";

In fact, the ternary operator can be extended and used. 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 use the string operation symbol (" .") 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 In this case, it is indeed too simple, 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 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 the if statement. The syntax of the following statements is 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 three When using meta-operators, it is recommended to use print statements instead of echo statements.

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 assignment is 'wangjinbo' Otherwise, the 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 two Yuan, ternary 'wangjinbo' or 'wjb' alone cannot form a meaningful expression;

The correct understanding is: when $_GET['abc'] is empty (that is, whether, in PHP' , null, 0, undifine, are all equivalent to the Boolean value false), assign $str to 'wangjinbo', otherwise assign it to 'wjb';

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