PHP-A
starting-syntax-code-examples
php
"PHP is an HTML-embedded scripting language. Much of its syntax is
borrowed from C, Java and Perl with a couple of unique PHP-specific features
thrown in. The goal of the language is to allow web developers to write
dynamically generated pages quickly."
This is generally a good definition of PHP. However, it does
contain a lot of terms you may not be used to. Another way to think of PHP is a
powerful, behind the scenes scripting language that your visitors won't see!
When someone visits your PHP webpage, your web server processes
the PHP code. It then sees which parts it needs to show to visitors(content and
pictures) and hides the other stuff(file operations, math calculations, etc.)
then translates your PHP into HTML. After the translation into HTML, it sends
the webpage to your visitor's web browser.
php - syntax
- Syntax - The rules that must be followed to write properly structured code.
PHP's syntax and semantics are similar to most other programming
languages (C, Java, Perl) with the addition that all PHP code is contained with
a tag, of sorts. All PHP code must be contained within the following...
or the shorthand PHP tag that
requires shorthand support to be enabled
on your server...
<?
?>
If you are writing PHP scripts and plan on distributing them, we
suggest that you use the standard form (which includes the ?php) rather than
the shorthand form. This will ensure that your scripts will work, even when
running on other servers with different settings.
how to save your php pages
If you have PHP inserted into your HTML
and want the web browser to interpret it correctly, then you must save the file
with a .php extension, instead of the standard .html extension. So be sure to check that
you are saving your files correctly. Instead of index.html, it should be index.php if there is PHP code in the file.
example simple html & php page
Below is an example of one of the
easiest PHP and HTML page that you can create and still follow web standards.
PHP and HTML Code:
<html>
<head>
<title>My First PHP Page</title>
</head>
<body>
<?php
echo "Hello World!";
?>
</body>
</html>
As you may or may not have noticed in
the above example, there was a semicolon after the line of PHP code. The
semicolon signifies the end of a PHP statement and should never be forgotten.
For example, if we repeated our "Hello World!" code several times,
then we would need to place a semicolon at the end of each statement.
PHP and HTML Code:
<html>
<head>
<title>My First PHP Page</title>
</head>
<body>
<?php
echo "Hello World! ";
echo "Hello World! ";
echo "Hello World! ";
echo "Hello World! ";
echo "Hello World! ";
?>
</body>
</html>
white space
As with HTML, whitespace is ignored
between PHP statements. This means it is OK to have one line of PHP code, then
20 lines of blank space before the next line of PHP code. You can also press
tab to indent your code and the PHP interpreter will ignore those spaces as
well.
PHP and HTML Code:
<html>
<head>
<title>My First PHP Page</title>
</head>
<body>
<?php
echo "Hello World!";
echo "Hello World!";
?>
</body>
</html>
php - variables
If you have never had any programming,
Algebra, or scripting experience, then the concept of variables might be a new concept to you. A
detailed explanation of variables is beyond the scope of this tutorial, but
we've included a refresher crash course to guide you.
A variable is a means of storing a
value, such as text string "Hello World!" or the integer value 4. A
variable can then be reused throughout your code, instead of having to type out
the actual value over and over again. In PHP you define a variable with the
following form:
- $variable_name = Value;
If you forget that dollar sign at the
beginning, it will not work. This is a common mistake for new PHP programmers!
Note: Also, variable names are case-sensitive, so use the exact
same capitalization when using a variable. The variables $a_number and $A_numberare
different variables in PHP's eyes.
a quick variable example
Say that we wanted to store the values
that we talked about in the above paragraph. How would we go about doing this?
We would first want to make a variable name and then set that equal to the
value we want. See our example below for the correct way to do this.
PHP Code:
<?php
$hello = "Hello World!";
$a_number = 4;
$anotherNumber = 8;
?>
Note for programmers: PHP does not
require variables to be declared before being initialized.
php variable naming conventions
There are a few rules that you need to
follow when choosing a name for your PHP variables.
- PHP variables must start with a letter or underscore "_".
- PHP variables may only be comprised of alpha-numeric characters and underscores. a-z, A-Z, 0-9, or _ .
- Variables with more than one word should be separated with underscores. $my_variable
- Variables with more than one word can also be distinguished with capitalization. $myVariable
php - echo
As you saw in the previous lesson, the
PHP command echo is a means of outputting text to the
web browser. Throughout your PHP career you will be using the echo command more
than any other. So let's give it a solid perusal!
outputting a string
To output a string, like we have done
in previous lessons, use PHP echo. You can place either a string variable or
you can use quotes, like we do below, to create a string that the echo function
will output.
PHP Code:
<?php
$myString = "Hello!";
echo $myString;
echo "<h5>I love using
PHP!</h5>";
?>
In our second echo statement we use echo to write a valid Header 5 HTML
statement. To do this we simply put the
at the beginning of the string and closed it at the end of the string. Just because you're using PHP to make web pages does not mean you can forget about HTML syntax!
Careful when echoing quotes!
It is pretty cool that you can output
HTML with PHP. However, you
must be careful when using HTML code or any other string that includes quotes!Echo
uses quotes to define the beginning and end of the string, so you must use one
of the following tactics if your string contains quotations:
- Don't use quotes inside your string
- Escape your quotes that are within the string with a backslash. To escape a quote just place a backslash directly before the quotation mark, i.e. \"
- Use single quotes (apostrophes) for quotes inside your string.
See our example below for the right and
wrong use of echo:
PHP Code:
<?php
// This won't work because of the quotes around
specialH5!
echo "<h5
class="specialH5">I love using
PHP!</h5>";
// OK because we escaped the quotes!
echo "<h5 class=\"specialH5\">I
love using PHP!</h5>";
// OK because we used an apostrophe '
echo "<h5 class='specialH5'>I
love using PHP!</h5>";
?>
echoing variables
Echoing variables is very easy. The PHP
developers put in some extra work to make the common task of echoing all variables nearly foolproof! No
quotations are required, even if the variable does not hold a string. Below is
the correct format for echoing a variable.
PHP Code:
<?php
$my_string = "Hello Bob. My name is: ";
$my_number = 4;
$my_letter = a;
echo $my_string;
echo $my_number;
echo $my_letter;
?>
echoing variables and text strings
You can also place variables inside of
double-quoted strings (e.g. "string here and a $variable"). By
putting a variable inside the quotes (" ") you are telling PHP that
you want it to grab the string value of that variable and use it in the string.
The example below shows an example of this cool feature.
PHP Code:
<?php
$my_string = "Hello Bob. My name is: ";
echo "$my_string Bobettta <br />";
echo "Hi, I'm Bob. Who are you? $my_string <br />";
echo "Hi, I'm Bob. Who are you? $my_string Bobetta";
?>
By placing variables inside a string
you can save yourself some time and make your code easier to read, though it
does take some getting used to. Remember to use double-quotes, single-quotes
will not grab the value of the string. Single-quotes will just output the
variable name to the string, like )$my_string), rather than (Hello Bob. My name
is: ).
php echo - not a function
Echo is not a function, rather it is a
language construct. When you usefunctions
in PHP, they have a very particular form, which we will be going
over later. For now, just know that echo is a special tool that you'll come to
know and love!
php - string creation
Before you can use a string you have to
create it! A string can be used directly in a function or it can be stored in a
variable. Below we create the exact same string twice: first storing it into a
variable and in the second case we send the string directly to echo.
PHP Code:
$my_string = "4bizindia.com - Unlock your
potential!";
echo "4bizindia.com - Unlock your
potential!";
echo $my_string;
php - string creation single quotes
Thus far we have created strings using
double-quotes, but it is just as correct to create a string using single-quotes,
otherwise known as apostrophes.
PHP Code:
$my_string = '4bizindia.com - Unlock your
potential!';
echo '4bizindia.com - Unlock your
potential!';
echo $my_string;
php - string creation double-quotes
We have used double-quotes and will
continue to use them as the primary method for forming strings. Double-quotes
allow for many special escaped characters to be used that you cannot do with a
single-quote string. Once again, a backslash is used to escape a character.
PHP Code:
$newline = "A newline is \n";
$return = "A carriage return is
\r";
$tab = "A tab is \t";
$dollar = "A dollar sign is \$";
$doublequote = "A double-quote is
\"";
These escaped characters are not very
useful for outputting to a web page because HTML ignore extra white space. A
tab, newline, and carriage return are all examples of extra (ignorable) white
space. However, when writing to a file that may be read by human eyes these
escaped characters are a valuable tool!
php - string creation heredoc
The two methods above are the
traditional way to create strings in most programming languages. PHP introduces
a more robust string creation tool calledheredoc that lets the programmer create
multi-line strings without using quotations. However, creating a string using
heredoc is more difficult and can lead to problems if you do not properly code
your string! Here's how to do it:
PHP Code:
$my_string = <<<TEST
4bizindia.com
Webmaster Tutorials
Unlock your potential!
TEST;
echo $my_string;
There are a few very important things to remember when
using heredoc.
- Use <<< and some identifier that you choose to begin the heredoc. In this example we chose TEST as our identifier.
- Repeat the identifier followed by a semicolon to end the heredoc string creation. In this example that was TEST;
- The closing sequence TEST; must occur on a line by itself and cannot be indented!
Another thing to note is that when you
output this multi-line string to a web page, it will not span multiple lines
because we did not have any
tags contained inside our string! Here is the output made from the code above.
tags contained inside our string! Here is the output made from the code above.
php - operators
In all programming languages, operators are used to manipulate or
perform operations on variables and values. You have already seen the string
concatenation operator "." in the Echo Lesson and
the assignment operator "=" in pretty much every PHP example so far.
There are many operators used in PHP, so we have separated them
into the following categories to make it easier to learn them all.
- Assignment Operators
- Arithmetic Operators
- Comparison Operators
- String Operators
- Combination Arithmetic & Assignment Operators
assignment operators
Assignment operators are used to set a variable equal to a value
or set a variable to another variable's value. Such an assignment of value is
done with the "=", or equal character. Example:
- $my_var = 4;
- $another_var = $my_var;
Now both $my_var and $another_var contain the value 4. Assignments
can also be used in conjunction with arithmetic operators.
arithmetic operators
|
Operator
|
English
|
Example
|
|
+
|
Addition
|
2 + 4
|
|
-
|
Subtraction
|
6 - 2
|
|
*
|
Multiplication
|
5 * 3
|
|
/
|
Division
|
15 / 3
|
|
%
|
Modulus
|
43 % 10
|
HP Code:
$addition = 2 + 4;
$subtraction = 6 - 2;
$multiplication = 5 * 3;
$division = 15 / 3;
$modulus = 5 % 2;
echo "Perform addition: 2 + 4 = ".$addition."<br />";
echo "Perform subtraction: 6 - 2 = ".$subtraction."<br />";
echo "Perform multiplication: 5 * 3 = ".$multiplication."<br />";
echo "Perform division: 15 / 3 = ".$division."<br />";
echo "Perform modulus: 5 % 2 = " . $modulus
. ". Modulus is the remainder after the division operation has been performed.
In this case it was 5 / 2, which has a remainder of 1.";
Comparisons are used to check the
relationship between variables and/or values. If you would like to see a simple
example of a comparison operator in action, check out our If Statement
Lesson. Comparison operators are used inside conditional statements
and evaluate to either true or false.
Here are the most important comparison operators of PHP.
Assume: $x = 4 and $y = 5;
Assume: $x = 4 and $y = 5;
|
Operator
|
English
|
Example
|
Result
|
|
==
|
Equal
To
|
$x
== $y
|
false
|
|
!=
|
Not
Equal To
|
$x
!= $y
|
true
|
|
<
|
Less
Than
|
$x
< $y
|
true
|
|
>
|
Greater
Than
|
$x
> $y
|
false
|
|
<=
|
Less
Than or Equal To
|
$x
<= $y
|
true
|
|
>=
|
Greater
Than or Equal To
|
$x
>= $y
|
false
|
string operators
As we have already seen in the Echo Lesson,
the period "." is used to add two strings together, or more
technically, the period is the concatenation operator for strings.
PHP Code:
$a_string = "Hello";
$another_string = " Billy";
$new_string = $a_string . $another_string;
echo $new_string . "!";
In programming it is a very common task
to have to increment a variable by some fixed amount. The most common example
of this is a counter. Say you want to increment a counter by 1, you would have:
- $counter = $counter + 1;
However, there is a shorthand for doing
this.
- $counter += 1;
This combination assignment/arithmetic
operator would accomplish the same task. The downside to this combination
operator is that it reduces code readability to those programmers who are not
used to such an operator. Here are some examples of other common shorthand
operators. In general, "+=" and "-=" are the most widely
used combination operators.
|
Operator
|
English
|
Example
|
Equivalent
Operation
|
|
+=
|
Plus
Equals
|
$x
+= 2;
|
$x
= $x + 2;
|
|
-=
|
Minus
Equals
|
$x
-= 4;
|
$x
= $x - 4;
|
|
*=
|
Multiply
Equals
|
$x
*= 3;
|
$x
= $x * 3;
|
|
/=
|
Divide
Equals
|
$x
/= 2;
|
$x
= $x / 2;
|
|
%=
|
Modulo
Equals
|
$x
%= 5;
|
$x
= $x % 5;
|
|
.=
|
Concatenate
Equals
|
$my_str.="hello";
|
$my_str
= $my_str . "hello";
|
pre/post-increment & pre/post-decrement
This may seem a bit absurd, but there
is even a shorter shorthand for the common task of adding 1 or subtracting 1
from a variable. To add one to a variable or "increment" use the
"++" operator:
- $x++; Which is equivalent to $x += 1; or $x = $x + 1;
To subtract 1 from a variable, or
"decrement" use the "--" operator:
- $x--; Which is equivalent to $x -= 1; or $x = $x - 1;
In addition to this
"shorterhand" technique, you can specify whether you want to
increment before the line of code is being executed or after the line has
executed. Our PHP code below will display the difference.
PHP Code:
$x = 4;
echo "The
value of x with post-plusplus = " . $x++;
echo
"<br /> The value of x after the post-plusplus is " .
$x;
$x = 4;
echo
"<br />The value of x with with pre-plusplus = " .
++$x;
echo
"<br /> The value of x after the pre-plusplus is " .
$x;
using comments in php
Comments in PHP are similar to comments that are used in HTML. The
PHP comment syntax always begins with a special character sequence and all text
that appears between the start of the comment and the end will be ignored.
In HTML a comment's main purpose is to
serve as a note to you, the web developer or to others who may view your
website's source code. However, PHP's comments are different in that they will
not be displayed to your visitors. The only way to view PHP comments is to open
the PHP file for editing. This makes PHP comments only useful to PHP
programmers.
In case you forgot what an HTML comment
looked like, see our example below.
HTML Code:
<!--
This is an HTML Comment -->
hp comment syntax: single line comment
While there is only one type of comment
in HTML, PHP has two types. The first type we will discuss is the single line
comment. The single line comment tells the interpreter to ignore everything
that occurs on that line to the right of the comment. To do a single line
comment type "//" or "#" and all text to the right will be
ignored by PHP interpreter.
PHP Code:
<?php
echo "Hello World!"; // This will print
out Hello World!
echo "<br />Psst...You can't see
my PHP comments!"; // echo "nothing";
// echo "My name is Humperdinkle!";
# echo "I don't do anything
either";
?>
php comment syntax: multiple line comment
Similiar to the HTML comment, the
multi-line PHP comment can be used to comment out large blocks of code or
writing multiple line comments. The multiple line PHP comment begins with
" /* " and ends with " */ ".
PHP Code:
<?php
/* This Echo
statement will print out my message to the
the place in
which I reside on. In other words, the World. */
echo
"Hello World!";
/* echo
"My name is Humperdinkle!";
echo "No
way! My name is Uber PHP Programmer!";
*/
?>
php include
Without understanding much about the details of PHP, you can save
yourself a great deal of time with the use of the PHP include command. include takes
a file name and simply inserts that file's contents into the script that issued
the includecommand.
Why is this a cool thing? Well, first
of all, this means that you can type up a common header or menu file that you
want all your web pages to include. When you add a new page to your site,
instead of having to update the links on several web pages, you can simply
change the Menu file.
an include example
Say we wanted to create a common menu
file that all our pages will use. A common practice for naming files that are
to be included is to use the ".php" extension. Since we want to
create a common menu let's save it as "menu.php".
menu.php Code:
<html>
<body>
<a
href="http://www.example.com/index.php">Home</a>
-
<a
href="http://www.example.com/about.php">About
Us</a> -
<a
href="http://www.example.com/links.php">Links</a>
-
<a href="http://www.example.com/contact.php">Contact
Us</a> <br />
index.php Code:
<?php
include("menu.php"); ?>
<p>This
is my home page that uses a common menu to save me time when I add
new pages to my
website!</p>
</body>
</html>
And we would do the same thing for "about.php", "links.php",
and "contact.php". Just think how terrible it would be if you had 15
or more pages with a common menu and you decided to add another web page to
that site. You would have to go in and manually edit every single file to add
this new page, but with include files you simply have to change
"menu.php" and all your problems are solved. Avoid such troublesome
occasions with a simple include file.
what do visitors see?
If we were to use the include command
to insert a menu on each of our web pages, what would the visitor see if they
viewed the source of "index.php"? Well, because the include command
is pretty much the same as copying and pasting, the visitors would see:
View Source of index.php to a Visitor:
<html>
<body>
<a
href="index.php">Home</a> -
<a
href="about.php">About Us</a> -
<a
href="links.php">Links</a> -
<a
href="contact.php">Contact Us</a> <br
/>
<p>This
is my home page that uses a common menu to save me time when I add
new pages to my
website!</p>
</body>
</html>
The visitor would actually see all the HTML code as one long line
of HTML code, because we have not inserted any new line characters. We did some
formatting above to make it easier to read. We will be discussing new line
characters later.
php require
Just like the previous lesson, the require command is used to
include a file into your PHP code. However there is one huge difference between
the two commands, though it might not seem that big of a deal.
equire vs include
When you include a file with the include command and PHP cannot find it you
will see an error message like the following:
PHP Code:
<?php
include("noFileExistsHere.php");
echo "Hello World!";
?>
PHP Code:
<?php
require("noFileExistsHere.php");
echo "Hello World!";
?>
The if statement is necessary for most programming, thus it is
important in PHP. Imagine that on January 1st you want to print out "Happy
New Year!" at the top of your personal web page. With the use of PHP if
statements you could have this process automated, months in advance,
occuring every year on January 1st.
This idea of planning for future events is something you would
never have had the opportunity of doing if you had just stuck with HTML.
if statement example
The "Happy New Year" example
would be a little difficult for you to do right now, so let us instead start
off with the basics of the if statement. The PHP if statement tests to see if a
value is true, and if it is a segment of code will be executed. See the example
below for the form of a PHP if statement.
PHP Code:
$my_name =
"someguy";
if ( $my_name
== "someguy" ) {
echo "Your name is someguy!<br
/>";
}
echo
"Welcome to my homepage!";
- We first set the variable $my_name equal to "someguy".
- We next used a PHP if statement to check if the value contained in the variable $my_name was equal to "someguy"
- The comparison between $my_name and "someguy" was done with a double equal sign "==", not a single equals"="! A single equals is for assigning a value to a variable, while a double equals is for checking if things are equal.
- Translated into english the PHP statement ( $my_name == "someguy" ) is ( $my_name is equal to "someguy" ).
- $my_name is indeed equal to "someguy" so the echo statement is executed.
a false if statement
Let us now see what happens when a PHP
if statement is not true, in other words, false. Say that we changed the above
example to:
PHP Code:
$my_name = "anotherguy";
if ( $my_name == "someguy" ) {
echo
"Your name is someguy!<br />";
}
echo "Welcome to my homepage!";
Has someone ever told you, "if you work hard, then you will
succeed"? And what happens if you do not work hard? Well, you fail! This
is an example of an if/else conditional statement.
- If you work hard then you will succeed.
- Else, if you do not work hard, then you will fail.
How does this translate into something
useful for PHP developers? Well consider this:
Someone comes to your website and you
want to ask this visitor her name if it is her first time coming to your site.
With an if statement this is easy. Simply have a conditional statement to
check, "are you visiting for the first time". If the condition is
true, then take them to the "Insert Your Name" page, else let her
view the website as normal because you have already asked her for her name in
the past.
if/else an example
Using these conditional statements can
add a new layers of "cool" to your website. Here's the basic form of
an if/else statement in PHP.
PHP Code:
$number_three =
3;
if (
$number_three == 3 ) {
echo "The if statement evaluated to
true";
} else {
echo "The if statement evaluated to
false";
}
- We first made a PHP variable called $number_three and set it equal to 3.
- In this example we compared a variable to an integer value. To do such a comparison we use "==", which in English means "Is Equal To".
- $number_three is indeed Equal To 3 and so this statement will evaluate to true.
- All code that is contained between the opening curly brace "{" that follows the if statement and the closing curly brace "}" will be executed when the if statement is true.
- The code contained within the else segment will not used.
execute else code with false
On the other hand, if the if statement was false, then the code contained in
the else segment would have been executed. Note that the code within the if andelse cannot both be executed, as the if
statement cannot evaluate to both true and false at one time! Here is what
would happen if we changed to $number_three to anything besides the number 3.
PHP Code:
$number_three = 421;
if ( $number_three == 3 ) {
echo
"The if statement evaluated to true";
} else {
echo
"The if statement evaluated to false";
}
An if/else statement is great if you only need to check for one
condition. However, what would you do if you wanted to check if your $employee variable
was the company owner Bob, the Vice President Ms. Tanner, or a regular
employee? To check for these different conditions you would need the elseif statement.
php - elseif what is it?
An if statement is made up of the keyword
"if" and a conditional statement (i.e. $name == "Ted").
Just like an if statement, an elseif statement also contains a conditional
statement, but it must be preceded by an if statement. You cannot have an elseif statement without first having an if statement.
When PHP evaluates your
If...elseif...else statement it will first see if the If statement is true. If
that tests comes out false it will then check the first elseif statement. If
that is false it will either check the next elseif statement, or if there are
no more elseif statements, it will evaluate the else segment, if one exists (I
don't think I've ever used the word "if" so much in my entire life!).
Let's take a look at a real world example.
php - using elseif with if...else
Let's start out with the base case.
Imagine we have a simpler version of the problem described above. We simply
want to find out if the employee is the Vice President Ms. Tanner. We only need
an if else statement for this part of the
example.
PHP Code:
$employee = "Bob";
if($employee == "Ms. Tanner"){
echo
"Hello Ma'am";
} else {
echo
"Morning";
}
PHP Code:
$employee =
"Bob";
if($employee ==
"Ms. Tanner"){
echo "Hello Ma'am";
}
elseif($employee == "Bob"){
echo "Good Morning
Sir!";
}else {
echo "Morning";
}
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