overview.md

Overview

This is an overview of the built-in PHP language features and its basic syntax so you have better understanding of which chapters has been introduced so far.

PHP in a nutshell

• Scripting language
• Procedural and object oriented language
• Dynamically (weakly) typed
• Syntax similar to C, C++, C#, Java and Perl
• Imperative language
• PHP has closures

Hello world

File hello.php:

<?php

echo 'Hello world.';

can be run from the command line with:

php hello.php

Operators

Arithmetic operators

Operator	Name	Result
-$a	negation	Opposite of $a.
$a + $b	addition	Sum of $a and $b.
$a - $b	Subtraction	Difference of $a and $b.
$a * $b	Multiplication	Product of $a and $b.
$a / $b	division	Quotient of $a and $b.
$a % $b	modulus	Remainder of $a divided by $b.
$a ** $b	Exponentiation	Result of raising $a to the $b'th power.

Comparison operators

Operator	Name	Result
$a == $b	Equal	TRUE if $a is equal to $b after type juggling.
$a === $b	Identical	TRUE if $a is equal to $b, and they are of the same type.
$a != $b	Not equal	TRUE if $a is not equal to $b after type juggling.
$a <> $b	Not equal	TRUE if $a is not equal to $b after type juggling.
$a !== $b	Not identical	TRUE if $a is not equal to $b, or they are not of the same type.
$a < $b	Less than	TRUE if $a is strictly less than $b.
$a > $b	Greater than	TRUE if $a is strictly greater than $b.
$a <= $b	Less than or equal to	TRUE if $a is less than or equal to $b.
$a >= $b	Greater than or equal to	TRUE if $a is greater than or equal to $b.

Logical operators

Operator	Name	Result
$a and $b	And	TRUE if both $a and $b are TRUE.
$a or $b	Or	TRUE if either $a or $b is TRUE.
$a xor $b	Xor	TRUE if either $a or $b is TRUE, but not both.
! $a	Not	TRUE if $a is not TRUE.
$a && $b	And	TRUE if both $a and $b are TRUE.
`$a		$b`

Assignment operators

Operator	Description
=	Set a value to variable
+=	Addition of numeric value to variable
.=	Add string to variable

Declarations

• $i = 1; - assign value to variable
• define('FOO', 'something'); - define a constant

Functions

// A simple function
function functionName() {}

// A function with parameters
function functionName($param1, $param2) {}

Anonymous functions (closures)

<?php
echo preg_replace_callback('~-([a-z])~', function ($match) {
    return strtoupper($match[1]);
}, 'hello-world');
// outputs helloWorld

// Anonymous function variable assignment example
$greet = function($name) {
    printf("Hello %s\r\n", $name);
};
$greet('World');

// Inherit
$message = 'hello';

// Without "use" keyword
$example = function () {
    var_dump($message);
};
echo $example();

// Inherit $message
$example = function () use ($message) {
    var_dump($message);
};
echo $example();

Variadic functions

<?php
function sum(...$nums)
{
    return array_sum($nums);
}

Control structures

If

if $x > 0 {
    return $x;
} else {
    return -$x;
}

Loops

// for
for ($i = 1; $i<10; $i++) {}

// while
while ($i < 10) {}

// do while
$i = 0;
do {
    echo $i;
} while ($i > 0);


// foreach
foreach ($array as $key => $value) {}

Switch

// switch statement
switch ($operatingSystem) {
    case 'darwin':
        echo 'Mac OS Hipster';
        break;
    case 'linux':
        echo 'Linux Geek';
        break;
    default:
        // Windows, BSD, ...
        echo 'Other';
}

Arrays

$array = [
    "foo" => "bar",
    "bar" => "foo",
];

Operations on arrays

Operator	Name	Result
$a + $b	Union	Union of $a and $b.
$a == $b	Equality	TRUE if $a and $b have the same key/value pairs.
$a === $b	Identity	TRUE if $a and $b have the same key/value pairs in the same order and of the same types.
$a != $b	Inequality	TRUE if $a is not equal to $b.
$a <> $b	Inequality	TRUE if $a is not equal to $b.
$a !== $b	Non-identity	TRUE if $a is not identical to $b.

Built-in types

Type
boolean
integer
float
string
array
object
resource
NULL

Errors

PHP errors

<?php
// Turn off all error reporting
error_reporting(0);

// Report simple running errors
error_reporting(E_ERROR | E_WARNING | E_PARSE);

// Reporting E_NOTICE can be good too (to report uninitialized
// variables or catch variable name misspellings ...)
error_reporting(E_ERROR | E_WARNING | E_PARSE | E_NOTICE);

// Report all errors except E_NOTICE
error_reporting(E_ALL & ~E_NOTICE);

// Report all PHP errors (see changelog)
error_reporting(E_ALL);

// Report all PHP errors
error_reporting(-1);

// Same as error_reporting(E_ALL);
ini_set('error_reporting', E_ALL);

Exceptions

function inverse($x)
{
    if (!$x) {
        throw new Exception('Division by zero.');
    }

    return 1/$x;
}

try {
    echo inverse(5) . "\n";
} catch (Exception $e) {
    echo 'Caught exception: ',  $e->getMessage(), "\n";
} finally {
    echo "This is always executed.\n";
}