PHP - Syntax Overview
Topics to be covered
We will cover the following topics in this lesson
- Syntax Overview
- How Commenting works in PHP
- Outstanding Features of PHP
- Hello World
PHP - Syntax Overview
<?php Some code here ?>
<?phpis beginning tag to inform the parsing engine that PHP code starts from here whereas the
?>is end of code tag.
Anything that lies between these two tags will be considered PHP code. However within these tags HTML code can be inserted too and PHP engine will parse it smoothly, the way of doing so is:
Create a new file
overview.php in your project directory and add the following code.
<?php $thing = "Box"; echo "This is a " . $thing . "and its color is <font color=red> RED "; ?>
$thing = "Box";defines a string variable that is assigned the value of
echo "This is a " . $thing . "and its color is <font color=red> RED </font>";prints a string that uses the variable value and some HTML mark.
Run the following code to start the built-in PHP server in the project directory
php -S localhost:8000
- The above command starts the built-in server on PORT number
Load the following URL into your web browser
You should be able to see the following results
This is a Box and its color is RED
As shown above, HTML code can be inserted inside the
echo statement within the quotes but as soon as you break the code you are back to PHP area and as long as semi colon is not used it will be read as one statement only thus it will return the output as shown above.
How Commenting works in PHP
As with any other programming language and web scripting PHP also provides option for adding comments within the code.
A comment is basically any line or segment in the code that doesn't render on browser or when executed rather it is there for the code reader to understand instruction given by the coder.
It is mostly used for the coder himself for his own reference as well or his team so when he open the code after a while he knows what the line or segment below does. There are basically two types of commenting in PHP and as many as 3 styles can be used, for instance:
Single Line Comments
Single line comment example 1:
<?php # This is my first code. Below syntax will output Hello World! in web browser echo "Hello World!"; ?>
# This...the hash symbol before the string tells the PHP compiler that this is a comment.
Single line comment example 2:
<?php // This is my first code in PHP. Below syntax will output Hello World! In web browser echo "Hello World!"; ?>
// Thisthe double forward slashes tell the PHP compiler that this is a comment. The double forward slashes is more commonly used compared to the hash symbol.
Multiple Lines Comments
Multiple lines commenting using standard method:
<?php /* Hi, this is my first ever code that I have written in PHP and it is about orthodox Hello World code */ echo "Hello World!"; ?>
/*marks the beginning of the multiple comment. Anything that follows can span a number of lines and will be considered a comment.
*/marks the end of our multiple comment.
Using single line commenting characters as multiple lines commenting example 1:
<?php // First line of comment // Second line of comment echo "it works!"; ?>
Using single line commenting characters as multiple lines commenting example 2:
<?php # First line of comment # Second line of comment echo "it works!"; ?>
Using single line commenting characters as multiple lines commenting example 3:
<?php // First line of comment # Second line of comment echo "it works!"; ?>
Sensitivity and Insensitivity
Whitespace: PHP is mostly not sensitive to whitespaces, Whitespace means any character which is invisible in console but takes a space in code, such as a space, tab or carriage returns (such as EOL characters). So as long as a semi colon is not inserted at the end of statement PHP will parse it as a single line or same syntax even if you have passed return carriage.
$variable = 18 + 18;
Above is an example of single line syntax written with single spaces
$variable = 18 + 18 ;
Above is an example of single line syntax written with multiple tabs
$variable = 18 + 18 ;
Above is an example of single line syntax broken in to multiple lines with return carriage.
In all of the above examples PHP will parse the statement is a single syntax and will not process spaces or tabs neither it will consider carriage return as next or new syntax.
Case Sensitive: PHP is a case sensitive language so any variable or anything case sensitive in the code segment will work according to the case sensitivity rules.
<?php $room = 303; echo "Your room # is $room<br>"; echo "Your room # is $RooM<br>"; ?>
$room = 303;defines a variable
$roomthat is all lower case letters.
echo "Your room # is $room<br>";prints the value of the variable
echo "Your room # is $RooM<br>";prints the value of the variable
$RooM. Notice we the second variable used upper case letter
Rand upper case letter
Mat the end.
The above code outputs the following
Your room # is 303 Your room # is
Because variable with capital
M has not been defined.
The Terminator of Statement
As discussed above, PHP syntax EOL is determined by a semi colon at the end of the syntax instead of return carriage nor any other EOL character used in other languages.
<?php $room = 88 $floor = "13th" echo "Room # $room is on $floor" ?>
Above code will return error instead of giving out desired output
<?php $room = 88; $floor = "13th"; echo "Room # $room is on $floor floor"; ?>
Above code is written with proper PHP EOL (semi colon) and would output desired result.
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