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PHP Variables

In PHP, unlike other programming languages you can declare a variable or allocate variable storage space without worrying about the type of data that will be stored in it. Thus values are used when data in your script becomes available and can change during the lifetime of that specific script or when passed to another script.

In general PHP variable declaration starts with the character ($) and that can be followed by a combination of numbers, underscore and letters. Note however that, variable names can not have spaces otherwise it is going to give an error. Bellow are examples of valid variable declarations:

    $b;
    $b_small_letter;
    $123_passed_value;

As you may have already read, every PHP statement has to end with a semicolon (;) or otherwise known as instruction terminator

To assign a value to a variable, you simply do the following:

 $first_name = “Mununga”;

This statement tells the compiler to store the string “Mununga” in the space allocated to $first_name;
To print the content of that variable you would use the following statement:

 echo $first_name

which in this case, the compiler will interpret as

 echo “Mununga”;

Testing the data type of a variable

As soon as a value is assigned to the variable, you can test to see what kind of data is stored in it. The reason you may want to test the data type is that because PHP does not define the variable data type, that variable will only assume the data type after a value had been assigned. Under normal circumstances, the variable with a name $first_name would be expected to carry a string of Alfa-numeric value or string, but in PHP there is nothing to prevent anyone from assigning a number to the variable and the only way for you to know what is in it is to test the data type of its value.

To test the variable data type you use the following statement:

 echo gettype($first_name);

This will return one of the following data type:

Integer – if the value in the variable is a whole number

Object – if the value in the variable is an instance of a classs

String – if the value in the variable is a collection of Alfa-numeric characters

Double – if the value in the variable is a floating point number or decimal number

Boolean if the value in the variable is either TRUE or FALSE

Array – if the values in the variable are an ordered set of keys and values

By default, if the variable is not assigned a value, the statement will return the value NULL, meaning there is nothing in the allocated storage space.

Changing the data type of the variable

There maybe rare cases when you need to change the data type of the variable. Let us say you assigned a variable named river_depth as Double, but somehow you need to embed the value in a string for the readers you would do the following:

        $river_depth = 9.78;
        echo gettype($river_depth);  // displays the data type : Double;
        settype($river_depth, ‘String’); // changes the data type to String
        echo gettype($river_depth); // displays : String

You can also change the data type by a method widely known as casting . This means instead of using the settype keyword, you just put the data type in brackets in front of the variable. This will change the data type of the variable to the type indicated inside the brackets.
For Example, to convert $river_depth to integer you woul do the following:

echo (interger) $river_depth;

if the current value of river_depth is 9.78, this will display 10. thus it will convert the number to the nearest whole number and display that.

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PHP Variables

Testing the data type of a variable

Changing the data type of the variable

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