Detailed explanation of php ternary operator and if

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.

Recommended manual: php complete self-study manual

This article compares and explains the ternary operator and if...else... in detail. I hope to be helpful.

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 the ternary operator of PHP

This sentence The meaning is the same as

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.

Appropriate use of the ternary operator in PHP programs can make the script 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 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 be connected using string operation symbols ("."), 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 ternary operator used in nesting is not very readable, and there may be problems with maintaining the code in the future, but compared with "if...else" and the like Process statement, in the above situation, 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 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 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 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 value is assigned to 'wjb';

Because one: == should be used to judge equality;

Cause 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:

$_GET['abc'] is a null value (that is, whether (false), ' ', null, 0, and undifine in PHP are all equivalent to the Boolean value false). At this time, $str is assigned the value 'wjb' , otherwise the value is 'wangjinbo';

Note:

When there is no condition in the IF statement condition, the content itself $_GET['abc'] is true, the condition is established, and the str value is 'wangjinbo' ', otherwise the value is 'wjb'; when there is no clear value of true, true means there is a value, and false means there is no value.

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