PHP: Lesson 1

Key topics

• Using PHPinfo
• Variables
• Variable Naming Conventions
• Strings and Numbers
• For Loops
• While Loops
• Initialising Variables
• echo statement
• Differences between double and single quotes

Key Operators

• The assignment operator (=)
• The concatenation operator (.)
• The increment concatenation operator (.=)
• The addition operator (+)
• The addition increment operator (++)

Key terms

• Variable Naming Conventions
• Initialising Variables
• Concatentation
• Interpolation
• Statement Blocks

Get PHP Configuration

echo phpinfo();

Writing Comments

<?php //This is a single line comment /* * This is a multline * Comment - note it starts with a backslash and asterisk * and ends with an asterisk and backslash */ # This is a single line comment. I use it to comment out a line of code ?>

Hello World

<?php //Simple Example - note semi-colon at end of statement echo "Hello World"; //Simple example of including a tag echo "<hr />"; //Concatentation example - note use of . (dot) concatentation operator echo "Hello" . " " . "World" ?>

Introducing Variables and Strings

<?php /* * Note dollar sign to indicate variable * Text in PHP is referred to as a 'string' * All text is wrapped in either single or double quotes * In this example, the string "Hello World" is ASSIGNED to the variable $strGreeting */ $strGreeting = "Hello World."; echo $strGreeting; $strMessage = "This is PHP calling"; //Concatenating the two strings and echo'ing out in a single statement echo $strGreeting . $strMessage; //echo out a line for demonstration purposes echo "<hr />"; //note there was no space in html that was output, so you could write: echo $strGreeting . " " . $strMessage; /* * Formatting source - the following looks the same in the browser * but when you reveal source you will see they are on different lines to * assist in formatting and debugging * The \n is an ESCAPE sequence to indicate a new line should be placed in the soruce * You can also use it when sending plain text emails */ $strGreeting = "Hello World.\n"; $strMessage = "This is PHP calling\n"; echo $strGreeting; ?>

Variables within Strings

<?php /* * You can place variables within strings * Known as INTERPOLATION */ $strName = "John"; echo "Hello $strName"; //Output string must be in double quotes // But it does NOT work if the OUTPUT string is wrapped in single quotes $strName = "John"; echo 'Hello $strName'; //single quoted strings do not interpret the variables inside ?>

Generating a table

<?php /* * In this example we build up a string using the .= operator * This means add the string to the existing string * * Then we output the string at the end, this is usually quicker than echoing each single line */ $strHTML = ""; // Initialise the string, note a comment like this can be placed after semi-colon $strHTML .= "<table border = \"1\" >"; // note use of \ to escape the quotes in the border attribute $strHTML .= "<tr>"; // Open the row tag $strHTML .= "<td>"; //Open the cell tag $strHTML .= "Hello World"; //put content into the cell tag $strHTML .= "</td>"; // close the cell tag $strHTML .= "</tr>"; // close the row tag $strHTML .= "</table>"; // close the table tag //Notice Indentation above which helps you keep track of each html element echo $strHTML; //table is now output ?>

While loop

<?php /* * Output a paragraph containing a simple string 10 times * Note all looped content with the braces {} * content within braces { ... } is known as a STATEMENT BLOCK */ $intCounterLimit = 10; // In $intCounter = 0; while ($intCounter < $intCounterLimit) { echo "<p>While Loop Counter is $intCounter</p>"; $intCounter++; // increment the $intCounter as the last thing you do in while loop //you could also written the longer form: $counter = $counter +1; } ?>

For loop

<?php /* * Output a paragraph containing a simple string 10 times */ $counterLimit = 10; for($i=0; $i < counterLimit; $i++) { echo "<p>For Loop Counter is $i</p>"; } ?>

Using FOR loop to generate rows in a table

<?php $strHTML = ""; // Initialise the string, note comment can be placed after semi-colon $strHTML .= "<table border = \"1\" >"; // note use of \ to escape the quotes in the border attribute //note table tag is OUTSIDE the LOOP for ($i = 0; $i < 10; $i++ ) { // open the for loop for the rows $strHTML .= "<tr>"; // Open the row tag $strHTML .= "<td>"; //Open the cell tag $strHTML .= "Hello World $i"; //put content into the cell tag and show counter $strHTML .= "</td>"; // close the cell tag $strHTML .= "</tr>"; // close the row tag } // close the for loop at end of each row // note closing table tag is OUTSIDE THE LOOP $strHTML .= "</table>"; // close the table tag echo $strHTML; //table is now output ?>