php-notes/PHP.md

PHP

Setup

1. Download [MAMP] (https://www.mamp.info/en/downloads/)
2. Double click .pkg file and follow prompts
3. Double click /Applications/MAMP/MAMP
4. Tell MAMP to where your files are
   • Click on Preferences
   • Click on Web Server
   • Click the folder icon next to "Document Root" and find a suitable directory to work out of
   • Click OK
5. In your Document Root, create index.php.
6. Go to http://localhost:8888/
   • If no file is specified in the URL after the port, MAMP will look for index.php
7. Error logs are in /Applications/MAMP/logs/
   • use tail -f php_error.log to watch the end of the log file in case something breaks
8. MAMP stands for Mac, Apache, MySQL, PHP
   • Mac
     • Your OS
   • Apache
     • A pre-build web server that serves static files
     • It is extendable with various modules that allows it to do many things easily
   • MySQL
     • Your Database
   • PHP
     • A module for Apache that allows it to serve dynamic data

Basics

Tags

Because this is all run on top of Apache, the initial assumption is that we're serving static HTML files

• We need <?php ?> tags to show that we're writing PHP
• Think of this as if Apache/PHP is server.js and we're writing EJS

Instead of <%= %> you have <?= ?> or <?php echo ?>

Instead of <% %> you have <?php ?>

Comments

// single line comment

/*
multi
line
comment
*/

Declaring/Assigning variables

Use a $ before a variable name to tell php it is a variable. Assignment is standard.

<?php
	$my_first_var; //declare
	$my_first_var = 2; //assignment
	$my_second_var = 3; //declare and assign
	echo $my_first_var; //print this variable to the page
	echo $my_second_var; //print this variable to the page
?>

Data Types

PHP has the following basic data types:

Strings:

<?php
$x = "my string";
var_dump($x);
?>

Integers:

<?php
$x = 5985;
var_dump($x);
?>

Floats:

<?php
$x = 10.365;
var_dump($x);
?>

Booleans:

<?php
$x = true;
var_dump($x);
?>

Arrays:

<?php
$cars = array("Volvo","BMW","Toyota");
var_dump($cars);
?>

NULL:

<?php
$x = null;
var_dump($x);
?>

String Operators

Use a . or .= to combine strings. Works just like + and +=

<?php
	$first_part = "first part";
	$second_part = "second part";
	$concatenation = $first_part . " " . $second_part; //combine strings
	$concatenation .= ".  Appended value"; //append strings
	echo $concatenation;
?>

Some kinds of string interpolation work:

<?php
	$x = 5;
	echo "I have $x pizzas";
?>

Arithmetic Operators

<?php
	echo 1 + 1; //2
	echo 2 - 1; //1
	echo 3 * 2; //6
	echo 12 / 3; //4
	echo 5 % 2; //1 modulus
	echo 2 ** 3 //8 exponents
?>

Increment/Decrement Operators

<?php
	$x = 2;
	$x++; //increment by 1;
	echo $x;
	$x--; //decrement by 1;
	echo $x;
?>

Assignment Operators

<?php
	$my_var = 1;
	echo $my_var;
	$my_var += 3; //$my_var = $my_var + 1;
	echo $my_var;
	$my_var -= 2; //$my_var = $my_var - 1;
	echo $my_var;
	$my_var *= 2; //$my_var = $my_var * 2;
	echo $my_var;
	$my_var /= 2; //$my_var = $my_var / 2;
	echo $my_var;
?>

Conditionals

Formats

The traditional format works great:

<?php
	$x = 1;
	if($x > 2){
		echo "x > 2";
	}
	elseif($x < 2){
		echo "x > 2";
	}
	else{
		echo "x == 2";
	}
?>

If you have html and don't want to have lines that look like <?php } ?>, you can use the following style of if/else:

<?php $x = 1; ?>
<?php if($x > 2): ?>
	<code>x &gt; 2</code>
<?php elseif($ < 2): ?>
	<code>x &lt; 2</code>
<?php else: ?>
	<code>x == 2</code>
<?php endif; ?>

Comparison Operators

Equality:

<?php
	$x == $y; //equal
	$x === $y; //identical
	$x != $y; //not equal
	$x !== $y; //not identical
?>

Arithmetic:

<?php
	$x < $y; //less than
	$x > $y; //greater than
	$x <= $y; //less than or equal to
	$x >= $y; //greater than or equal to
?>

Logical Operators

<?php
	true && false //AND operator
	true || false //OR operator
?>

Arrays

Indexed Arrays

Standard array functionality

<?php
$cars = array("Volvo", "BMW", "Toyota");
$cars[4] = 'asdf'; //can be in indexes that don't yet exist
$cars[] = "added to end"; //pushes onto array
echo "I like " . $cars[0] . ", " . $cars[4] . " and " . $cars[5] . "."; //access arrays normally
echo count($cars); //prints length of array
print_r($cars); //prints contents of array in nicer format than var_dump
?>

Associative Arrays (hashes)

These are very similar to JavaScript objects, but are accessed like arrays:

<?php
	$age = array("Peter" => 35, "Ben" => 37, "Joe" => "43"); //declare
	$age["Bob"] = 105; //add at a new position
	echo "Bob is " . $age['Bob'] . " years old.";
?>

Loops

While

<?php
$x = 1;

while($x <= 5) {
    echo "The number is: $x <br/>";
    $x++;
}
?>

Alternative syntax:

<ul>
	<?php $x = 1;?>
	<?php while($x <= 5): ?>
		<li><?= $x ?></li>
		<?php $x++ ?>
	<?php endwhile; ?>
</ul>

For

<?php
for ($x = 0; $x <= 10; $x++) {
    echo "The number is: $x <br/>";
}
?>

Alternative syntax:

<ul>
	<?php for ($x = 0; $x <= 10; $x++): ?>
	    <li>The number is: <?= $x ?></li>
	<?php endfor; ?>
</ul>

Foreach

This is like for of in JS:

<?php
$colors = array("red", "green", "blue", "yellow");

foreach ($colors as $key => $value) {
    echo $key . ": $value <br/>";
}
?>

Alternative syntax:

<?php $colors = array("red", "green", "blue", "yellow"); ?>
<?php foreach ($colors as $key => $value): ?>
	<?= $key ?>: <?=$value?><br/>
<?php endforeach ?>

This works for associative arrays:

<?php
$ages = array("Peter" => 35, "Ben" => 37, "Joe" => "43");

foreach ($ages as $key => $value) {
    echo $key . ": $value <br/>";
}
?>

Alternative syntax:

<?php $ages = array("Peter" => 35, "Ben" => 37, "Joe" => "43"); ?>
<?php foreach ($ages as $key => $value): ?>
	<?= $key ?>: <?=$value?> <br/>
<?php endforeach ?>