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Understanding precedence and associativity (p38)
Using variable handling functions (p39)
Making decisions with conditionals (p41)
switch statement (p44)
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Xem thêm: Học làm web (x4) - PHP: crash course 4
Understanding precedence and associativity (p38)
Using variable handling functions (p39)
– Testing and setting variable type (p39)
string gettype(mixed var);
bool settype(mixed var, string type);
mixed is pseudo-type, means many types are accepted.
Example,
$a = 56;
echo gettype($a).'<br />';
settype($a, 'float');
echo gettype($a).'<br />';
PHP also provides some specific type-testing functions. Each
takes a variable as an argument and returns either true or false. The functions
are
– is_array()—Checks whether the variable is an array
– is_double(), is_float(), is_real() (All the same
function)—Checks whether the variable is a float
– is_long(), is_int(), is_integer() (All the same
function)—Checks whether the variable is an integer
– is_string()—Checks whether the variable is a string
– is_bool()—Checks whether the variable is a boolean
– is_object()—Checks whether the variable is an object
– is_resource()—Checks whether the variable is a resource
– is_null()—Checks whether the variable is null
– is_scalar()—Checks whether the variable is a scalar—that
is, an integer, boolean,
string, or float
– is_numeric()—Checks whether the variable is any kind of
number or a numeric
Testing variable
status (p40)
bool isset(mixed var[,
mixed var[,…]])
This function takes a variable name as an argument and
returns true if it exists and false
otherwise. You can also pass in a comma-separated list of variables, and isset() will return true if all the variables are set.
You can wipe a variable out of existence by using its
companion function, unset(), which has the following prototype:
void unset(mixed var
[, mixed var [,…]])
The empty()
function checks to see whether a variable exists and has a nonempty, nonzero
value; it returns true or false accordingly. It has the following
prototype:
bool empty(mixed var);
These functions are handy when you need to make sure that
the user filled out the appropriate fields in the form.
Reinterpreting
variables (p41)
Converting type of variable:
int intval(mixed var[,
int base=10])
float floatval(mixed
var)
string strval(mixed
var)
Making decisions with conditionals (p41)
if statements (p41)
if ($totalqty == 0)
echo
'You did not order anything on the previous page!<br />';
Code blocks
if ($totalqty == 0) {
echo '<p
style="color:red">';
echo 'You did not order anything on the
previous page!';
echo '</p>';
}
else statements (p42)
if ($totalqty == 0) {
echo "You did not order anything on
the previous page!<br />";
} else {
echo htmlspecialchars($tireqty).'
tires<br />';
echo htmlspecialchars($oilqty).' bottles
of oil<br />';
echo htmlspecialchars($sparkqty).' spark
plugs<br />';
}
More…
if ($totalqty == 0) {
echo "You did not order anything on
the previous page!<br />";
} else {
if ($tireqty > 0)
echo
htmlspecialchars($tireqty).' tires<br />';
if ($oilqty > 0)
echo
htmlspecialchars($oilqty).' bottles of oil<br />';
if ($sparkqty > 0)
echo
htmlspecialchars($sparkqty).' spark plugs<br />';
}
elseif statements
(p43)
if ($tireqty < 10) {
$discount = 0;
} elseif (($tireqty >= 10) && ($tireqty <= 49)) {
$discount = 5;
} elseif (($tireqty >= 50) && ($tireqty <= 99)) {
$discount = 10;
} elseif ($tireqty >= 100) {
$discount = 15;
}
Note that you are free to type elseif or else if—versions
with or without a space are both correct.
Lab 4.
Make a simple calculator.
The result screenshot:
Requirements:
– Using HTML, CSS to design the web front-end
– Using if, else, or elseif to calculate (PHP)
– Allow following this guide https://steemit.com/programming/@ryal/build-a-simple-calculator-with-html-php-and-css-programming
– Put the lab on the your free hosting, test to make sure it
run well
– Push the lab up the your remote repository (Github, or
Gitlab)
switch statement (p44)
The switch statement works in a similar way to the if statement,
but it allows the condition to take more than two values. In an if statement,
the condition can be either true or false. In a switch statement, the condition
can take any number of different values, as long as it evaluates to a simple
type (integer, string, or float). You need to provide a case statement to handle
each value you want to react to and, optionally, a default case to handle any
that you do not provide a specific case statement for.
Lab 5. Apply switch statement.
Bob wants to know what forms of advertising are working for
him, so you can add a question to the order form. Insert this HTML into the
order form, and the form will to look like following:
<tr>
<td>How
did you find Bob's?</td>
<td><select name="find">
<option value = "a">I'm a regular
customer</option>
<option value = "b">TV advertising</option>
<option value = "c">Phone directory</option>
<option value = "d">Word of mouth</option>
</select>
</td>
</tr>
At the server side (back-end) using switch statement to handle for $find variable.
switch($find) {
case "a"
:
echo
"<p>Regular customer.</p>";
break;
case "b"
:
echo
"<p>Customer referred by TV advert.</p>";
break;
case "c"
:
echo
"<p>Customer referred by phone directory.</p>";
break;
case "d"
:
echo
"<p>Customer referred by word of mouth.</p>";
break;
default :
echo
"<p>We do not know how this customer found us.</p>";
break;
}
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Cập nhật [19/4/2019]
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Xem thêm: Học làm web (x4) - PHP: crash course 4