PHP basics

This tutorial will show you basic PHP syntax and its features. If you’re new to PHP read the most basic PHP tutorial to get started as quickly and painlessly as possible. For becoming modern PHP developer read and follow also PHP: The Right Way. Seriously.

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

Basic syntax

Hello world

File hello.php:



echo 'Hello, world.';

$ 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`	Or	TRUE if either $a or $b is TRUE.

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() {}

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

Anonymous functions (closures)


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


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 span="">; $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


// 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";
}

What is next?

Use php.net. It has a great and detailed manual for a lot of your PHP adventures.

Which Books are recommended for Learning PHP?

There are many books available for learning PHP. But lots of them can get quickly outdated. Here is a quick list of PHP books you should look into when learning PHP or extending your knowledge. Also keep in mind that writing a very good programming book can take several thousand hours so supporting their authors is nice way of saying thank you.

Free PHP Books

Official PHP manual - Offical PHP manual is available also for offline usage.
PHP: The Right Way - An easy-to-read, quick reference for PHP best practices, accepted coding standards, and links to authoritative PHP tutorials around the Web. PHP: The Right Way is also available as a PDF book.
PHP 5 Power Programming
PHP Best Practices - a short, practical guide for common and confusing PHP tasks.
PHP Essentials
PHP Internals Book
PHP Pandas - Aims to teach everyone how to be a web developer.
PHP Programming
PHP Security Guide
Practical PHP Programming
Practical PHP Testing
Survive The Deep End: PHP Security - PHP Security
Wikibooks PHP Programming - PHP Programming book on Wikibooks.
Using Libsodium in PHP Projects - A guide to using the libsodium PHP extension for modern, secure, and fast cryptography.

Paid PHP Books

What does INT(11) stands for in MySQL?

What does "size" in int(size) of MySQL mean?

Friday, August 24th, 2007 at 21:40 +0000 (UTC) by Alexander Kirk

I was always wondering what the size of numeric columns in MySQL was. Forgive me if this is obvious to someone else. But for me the MySQL manual lacks a great deal in this field.

TL;DR: It's about the display width. You only see it when you use ZEROFILL.

Usually you see something like int(11) in CREATE TABLE statements, but you can also change it to int(4).

So what does this size mean? Can you store higher values in a int(11) than in an int(4)?

Let's see what the MySQL manual says:

INT[(M)] [UNSIGNED] [ZEROFILL]
A normal-size integer. The signed range is -2147483648 to 2147483647. The unsigned range is 0 to 4294967295.

No word about the M. The entry about BOOL suggests that the size is not there for fun as it is a synonym forTINYINT(1) (with the specific size of 1).

TINYINT[(M)] [UNSIGNED] [ZEROFILL]
A very small integer. The signed range is -128 to 127. The unsigned range is 0 to 255.
BOOL, BOOLEAN
These types are synonyms for TINYINT(1). A value of zero is considered false. Non-zero values are considered true: […]

So TINYINT(1) must be different in some way from TINYINT(4) which is assumed by default when you leave the size out¹. Still, you can store for example 100 into a TINYINT(1).

Finally, let's come to the place of the manual where there is the biggest hint to what the number means:

Several of the data type descriptions use these conventions:
M indicates the maximum display width for integer types. For floating-point and fixed-point types, M is the total number of digits that can be stored. For string types, M is the maximum length. The maximum allowable value of M depends on the data type.

It's about the display width. The weird thing is, though², that, for example, if you have a value of 5 digits in a field with a display width of 4 digits, the display width will not cut a digits off.

If the value has less digits than the display width, nothing happens either. So it seems like the display doesn't have any effect in real life.

Now² ZEROFILL comes into play. It is a neat feature that pads values that are (here it comes) less than the specified display width with zeros, so that you will always receive a value of the specified length. This is for example useful for invoice ids.

So, concluding: The size is neither bits nor bytes. It's just the display width, that is used when the field hasZEROFILL specified.

If you see any more uses in the size value, please tell me. I am curious to know.

mysql> alter table a change a a tinyint(1); Query OK, 0 rows affected (0.09 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> insert into a values (100); Query OK, 1 row affected (0.00 sec) mysql> select * from a; +-----+ | a | +-----+ | 100 | +-----+ 1 row in set (0.00 sec)

² Some code to better explain what I described so clumsily.
mysql> create table b ( b int (4)); Query OK, 0 rows affected (0.25 sec)

mysql> insert into b values (10000); Query OK, 1 row affected (0.00 sec) mysql> select * from b; +-------+ | b | +-------+ | 10000 | +-------+ 1 row in set (0.00 sec) mysql> alter table b change b b int(11); Query OK, 1 row affected (0.00 sec) Records: 1 Duplicates: 0 Warnings: 0 mysql> select * from b; +-------+ | b | +-------+ | 10000 | +-------+ 1 row in set (0.00 sec) mysql> alter table b change b b int(11) zerofill; Query OK, 1 row affected (0.00 sec) Records: 1 Duplicates: 0 Warnings: 0 mysql> select * from b; +-------------+ | b | +-------------+ | 00000010000 | +-------------+ 1 row in set (0.00 sec) mysql> alter table b change b b int(4) zerofill; Query OK, 1 row affected (0.08 sec) Records: 1 Duplicates: 0 Warnings: 0 mysql> select * from b; +-------+ | b | +-------+ | 10000 | +-------+ 1 row in set (0.00 sec) mysql> alter table b change b b int(6) zerofill; Query OK, 1 row affected (0.01 sec) Records: 1 Duplicates: 0 Warnings: 0

mysql> select * from b; +--------+ | b | +--------+ | 010000 | +--------+ 1 row in set (0.00 sec)

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