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PHP is considered to be a weak typed language. In essence, this means that PHP does not require you to declare data types. Variables still have data types associated with them but you can do radical things like adding a string to an integer without resulting in an error. Type declarations can help you define what should occur so that you get the expected results.
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The first new feature I want
to cover is type declarations.
0:00
This simply means specifying which
type of variable is being set,
0:03
instead of allowing PHP to
set this automatically.
0:07
PHP is considered a weak typed language.
0:10
In essence, this means that PHP does not
require that you declare the data types.
0:14
Variables still have data types associated
with them, but you can do radical things,
0:19
like adding a string to an integer
without resulting in an error.
0:25
Type declarations can help you
define what should occur, so
0:29
that you get the expected results.
0:33
This can also make your
code easier to read.
0:35
We'll look at some
specific examples shortly.
0:37
Since PHP5, you can use type hinting
to specify the expected data types
0:40
of an argument in a function declaration,
but only in the declaration.
0:46
When you call the function,
PHP will check whether or
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not the arguments are of
the specified type.
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If not, the runtime will raise an error
and the execution will be halted.
0:57
Besides only being used
in function declarations,
1:02
we are also limited to basically two
types, a class name or an array.
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Here's an example.
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If we were to create a function for
enrolling students,
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we would require that the first argument
be an object of the class, Student, and
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the second argument to
be an array of classes.
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If we tried to pass just the name of
the student instead of an object,
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we would get a fatal error.
1:29
If we were to pass a single class
instead of an array of classes,
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we would also get an error.
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We are required to pass
a student object and an array.
1:38
If we were to try to check for a scalar
variable, such as a string, PHP5 expects
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it to be an object of the class,
string, not the variable type, string.
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With PHP7, we now have added scalar types.
1:55
Specifically, int,
float, string, and bool.
1:59
By adding scalar type hints and
enabling strict requirements, it is hoped
2:04
that more correct and self-documenting
PHP programs can be written.
2:08
It also gives you more control over your
code and can make the code easier to read.
2:13
By default, scalar type declarations
are non-strict, which means they attempt
2:18
to change the original type to match the
type specified in the type declaration.
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In other words, if you pass a string that
starts with a number into a function that
2:29
requires a float, it will grab
the number from the beginning and
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remove everything else.
2:39
Passing a float into a function that
requires an int will become simply an int.
2:40
Let's look at an example
of a non-strict type.
2:46
The getTotal function receives two
floats and adds them together,
2:49
while it returns the sum.
2:53
Without strict types turned on,
PHP attempts to cast or
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to change these arguments to match
the type specified in the function.
2:59
So when we call getTotal with non-strict
types using an int of two and
3:03
a string of one week, PHP converts
these to floats, the first argument
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would be changed to 2.0, and the second
argument would be changed to 1.0.
3:14
However, you will get a notice because
this is not a well formed numeric value.
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The function will then
return a value of three,
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which would be completely wrong
if we were trying to add days.
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When we call getTotal with the float
2.8 and the string of 3.2,
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PHP converts the string to
the float 3.2 with no notice,
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because it was a smooth conversion.
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It then returns a value of six.
3:43
When we call getTotal with non-strict
types using the float 2.5,
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and the integer 1, the integer gets
converted to the float 1.0 and
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the function returns 3.5.
3:56
Additionally, PHP7 gives us
the opportunity to enable strict mode
3:58
on a file-by-file basis.
4:03
We do this by declaring strict
types at the top of any given file.
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This must be the very first line,
even before name spaces.
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Declaring strict typing will ensure
that any function call made in that file
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strictly adheres to the type specified.
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Strict is determined by the file in
which the call to the function is made,
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not the file in which
the function is defined.
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If a type declaration mismatch occurs,
a fatal error is thrown, and
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we know that something is
not functioning as desired.
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Instead of allowing PHP to simply
guess at what we want to happen,
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allowing PHP to guess can cause seemingly
random and hard to diagnose issues.
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We'll look at catching and
handling errors in the next section.
4:46
But for now, let's take a look at
examples using strict types turned on.
4:49
When declare strict type
has been turned on,
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the first two calls that pass
a string will produce a fatal error.
4:56
The exception to strict typing
is shown in the third call.
5:00
If you pass an int as
an argument that is looking for
5:03
a float,
PHP will perform what is called widening,
5:07
by adding a dot zero to the end,
and the function returns 3.5.
5:11
PHP7 also supports return
type declarations,
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which support all the same
types as arguments.
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To specify the return type,
we add a colon, and then the type,
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right before the opening curly bracket.
5:26
If we specify the return type of float, it
will work exactly like it has been working
5:29
in the previous two examples, since the
type being returned was already a float.
5:34
Adding the return types allows you to
be sure that your function returns what
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you expected to return,
5:44
as well as make int easy to see
up front how the function works.
5:45
If we specify the return type
as int without strict type set,
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everything will work the same
as it did without a return type.
5:54
The only difference is that it will
force the return to be an int.
5:58
In the third call,
the return value will truncate to three
6:01
because the floating
point will be dropped.
6:05
If we turn strict types on,
we'll get a fatal type error.
6:09
In this case, we'll need to specifically
cast our return value as an int.
6:13
This will then return the truncated value.
6:18
The new type declarations can
make code easier to read and
6:21
forces things to be used
the way they were intended.
6:24
Some people prefer to use unit testing
to check for intended use instead.
6:28
Having automated tests for
your code is highly recommended, but
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you can use both unit tests and type
declarations working in harmony together.
6:36
Either way, PHP does not require
that you declare types, but
6:41
it can definitely make
code easier to read.
6:45
You can see right at the start of
a function what is required and
6:49
what is returned.
6:52
When you are working with declared
types with strict types turned on,
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here are a few things to remember.
6:57
Strict types are enabled or
disabled per file, not a php.ini setting.
7:00
Strict applies to the file in which
the call to the function is made,
7:07
not the file in which
the function is defined.
7:11
If strict is defined in test.php,
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all function calls made from
test.php have strict typing.
7:17
Integers will be widened into
floats by adding dot zero.
7:22
All other type conversions will error.
7:26
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