What does question mark mean in php

The question mark in PHP has many meanings: 1. The question mark used in tags is a delimiter, used to identify the beginning and end of PHP code, and has no actual program meaning; 2. In ternary operations The question mark in the symbol is used to select the specified condition as the branch of program execution. The syntax is "Condition 1? Condition 2: Condition 3".

The operating environment of this tutorial: windows10 system, PHP7.1 version, DELL G3 computer

What does the question mark in php mean

The role of question marks in php code can be roughly divided into two categories. One is the pair of tags "" used in PHP tags, and the other is used in the ternary operator The "?" operator in , like this: $a == 1?true:false.

• The question mark used in the tag only acts as a delimiter, that is, to identify the beginning and end of the PHP code, and has no substantial program meaning.

• The question mark in the ternary operator has a specific program meaning. Its expression method is probably: Condition 1? Condition 2: Condition 3, when condition 1 is true , the function of the question mark is to select condition 2 as the branch to continue execution of the program. That is to say, once the condition is established, condition two will be executed, otherwise condition three will be executed.

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 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 sentence. For example:

$a>$b ? print "a大于b" : print "a小于b";

In fact, the ternary operator can be extended. 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 are very obvious As you can see, 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.

At the same time, the ternary operator can also be used nested.

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