Specifications

Other Operators

In addition to the operators we have covered so far, there are a number of others.

The comma operator, , ,is used to separate function arguments and other lists of items. It is

normally used incidentally.

Two special operators, new and ->, are used to instantiate a class and to access class members,

respectively. These will be covered in detail in Chapter 6.

The array operators,

[], enable us to access array elements. They will be covered in Chapter 3.

There are three others that we will discuss briefly here.

The Ternary Operator

This operator, ?:, works the same way as it does in C. It takes the form

condition ? value if true : value if false

The ternary operator is similar to the expression version of an if-else statement, which is

covered later in this chapter.

A simple example is

($grade > 50 ? “Passed” : “Failed”);

This expression evaluates student grades to “Passed” or “Failed”.

The Error Suppression Operator

The error suppression operator, @, can be used in front of any expression, that is, anything that

generates or has a value. For example

$a = @(57/0);

Without the @ operator, this line will generate a divide-by-zero warning (try it). With the opera-

tor included, the error is suppressed.

If you are suppressing warnings in this way, you should write some error handling code to

check when a warning has occurred. If you have PHP set up with the

track_errors feature

enabled, the error message will be stored in the global variable $php_errormsg.

The Execution Operator

The execution operator is really a pair of operators: a pair of backticks (``) in fact. The back-

tick is not a single quote—it is usually located on the same key as the ~ (tilde) symbol on your

keyboard.

PHP will attempt to execute whatever is contained between the backticks as a command at the

command line of the server. The value of the expression is the output of the command.

Using PHP

ART I

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