PHP in a Nutshell

Automatic Type Conversion

As PHP is loosely typed (which means that a given variable can change its type as needed), it will automatically convert one type of variable to another whenever possible. Most data types are freely convertible to most other data types; this code illustrates that point:

    $mystring = "12";
    $myinteger = 20;
    print $mystring + $myinteger;

That script will output 32, despite the fact that one of the variables is a string and the other is an integer. PHP will convert the non-integer operand, $mystring, into an integer, and will find that it is, in fact, an integer inside a string. If PHP converts a string such as "wombat" to an integer, it becomes 0.

Problems with automatic conversion occur when either no meaningful conversion is possible, or when conversion yields unexpected results. For example, calling print on an array makes PHP print out Array; it doesn't automatically convert the array to a string of all its elements. An exception to this is treating an object like a string, and this is covered more deeply in Chapter 8.

Unexpected results occur when PHP converts values and produces unhelpful results. For example, converting from a boolean to a string will produce a 1 if the boolean is set to true, or an empty string if false. Consider this script:

    $bool = true;
    print "Bool is set to $bool\n";
    $bool = false;
    print "Bool is set to $bool\n";

That will output the following:

    Bool is set to 1
    Bool is set to

As you can see, it didn't print a 0 for false. To solve this ...