php-basics

PHP Basics

This topic we'll show the basic and the language essentials to start and app with PHP. PHP is intented to provide simplicity in development process.

Code Examples

Here

PHP tags

/*
<?php ?> - Standard Tags, enabled by default
<?= ?> - Echo Tags, Default PHP 5.4+
<? ?> - Short Tags, PHP Ini option - Default off
<% %> - ASP Tags, PHP Ini option - Default off, Removed on PHP 7.0
*/

Data Types

Scalar Types:

integer - a signed numeric value
boolean - a value that can be true or false
float - signed floating-point range numeric value
string - a collection of binary data

Composite Types:

array - container of mixed data, from scalar types to objects or arrays inside arrays
object - container of code and data. they are the basis of object oriented programming

Special Types:

resource - external resources that are not natively of PHP like file handling, image manipulation.
null - indicate variable that has no value and has set to the special value NULL or if the value hasn't been set on the variable.

Variables

//Store a value
$carOneValue = 1;
/* Reference carOneValue variable to the new $carOneValueReference.*/
$carOneValueReference = &$carOneValueReference;
//Change value to the two variables
$carOneValueReference = 100.80

Variable variables

$myVar = 'someValue';
$$myVar = 'anotherValue';
echo $someValue; //prints anotherValue

Variables as reference

$carOneValue = 1;
function sumCarValue(&$carValue, $plusValue = 0) {
  return $carValue = $carValue + $plusValue;
}
sumCarValue($carOneValue, 1000);
var_dump($carOneValue);

Check if variable exists

if (isset($someVar)) {
    //she exists
} else {
    //She didn't exists
}

//or check directly, i recommend avoid using 'else' as possibe in PHP
if (!isset($someVar)) {
    //she didn't exist
}

Converting data types (Type Casting)

$a = 1;
$a = (string) $a;

$b = 10.8;
$b = (int) $b;

$c = '10.82';
$c = (float) $c;

There are some functions to cast types if you prefer, see in the table below:

Tag	Description
intval()	Cast the given variable to an integer
floatval()	Cast the given variable to a float
strval()	Cast the given variable to a strin
boolval()	Cast the given variable to a boolean
settype()	Cast the given variable to a given type

Comment types

// Single line comments

# Single line comments

/* 
Multi-line
Comments
*/

/**
 * API Documentation Example
 *
 * @param string $bar
 */
function foo($bar) { }

Whitespace rules

• You cannot have any whitespace between <? and php
• You cannot break apart keywords (e.g.: whi le, fo r, and funct ion)
• You cannot break apart variable names and function names (e.g.:
• $var name and function foo bar())
• Heredoc and Nowdoc closing identifiers must not be preceded by
• anything, including whitespace.

Code Blocks

//If statements
if (expression) {
    //Some code here
} else {
    //Some other expressions here
}
//Function statements
function car() {
    //Some code here
}
//Function call
car();

Language Constructs - Output

Check on the php.net manual, because some constructors can accept parameters like a function

exit;
die; //a nickname for exit
echo;
return;
print;

Evaluation Constructs

empty();
eval();
include e include_once //generate warning if file not found
require e require_once //generate fatal error if file not found
isset()
unset()
list()

Magic constants

__LINE__;
__FILE__;
__DIR__;
__FUNCTION__;
__CLASS__;
__TRAIT__;
__METHOD__;
__NAMESPACE__;

Language operators

Bear in mind to check operator precende in PHP Manual. Assignment operator:

$a = 'by value';
$b = &$a;
echo $a;
echo PHP_EOL; //php end of line constant
echo $b;
echo PHP_EOL;
$b = 'Changed value in the reference variable';
echo $a;
echo PHP_EOL;
echo $b;

Arithmetic operator:

$plus = 2 + 2;
$minus = 2 - 2;
$multiplication = 2 * 2;
$division = 2 / 2;
$mod = 2 % 2;

Referencing values:

$a = 1;
$b = &$a;

Bitwise operator: With sprintf with leading zeros on the left and decbin, we can check the binary value of our two to check bits that are active or not and sum the result accoding to which operator we're using

// NOT - OPERATOR
$a = ~1; //0
// AND - Share the same bit active  
$a = 8;
$b = 10;
echo sprintf('%08s', decbin($a));
echo '<br>';
echo sprintf('%08s', decbin($b));
echo '<br>';
echo $a & $b; //8
//OR - OPERATOR
$a = 9;
$b = 10;
echo sprintf('%08s', decbin($a));
echo '<br>';
echo sprintf('%08s', decbin($b));
echo '<br>';
echo $a | $b; //11
//XOR - OPERATOR
$a = 9;
$b = 10;
echo sprintf('%08s', decbin($a));
echo '<br>';
echo sprintf('%08s', decbin($b));
echo '<br>';
echo $a ^ $b; //3

Bitwise multiplication & division:

//Multiplication by the power of 2
$x = 2;
echo $x << 1; // Outputs 4
echo $x << 2; // Outputs 8
//Division by the power of 2
$x = 4;
echo $x >> 1; // Outputs 2
echo PHP_EOL;
echo $x >> 2; // Outputs 1

Comparison operators

Equivalence:

'a' == 'b' //false
'1' == '1' //true

Identity:

'a' === 'b' //false
1 === '1' //false
1 === 1 //true

Not equivalent:

'a' != 'b' //true
'1' != '1' //false

Not identical:

'a' !== 'b' //true
'a' !== 'a' //false
1 !== '1' //true
1 !== 1 //false

Less than and less & equals to:

15 <= 15 //true
15 < 15 //false
15 < 16 //true

Greater than and greater & equals:

15 >= 15 //true
15 > 15 //false
16 > 15 //true

Spaceship operator:

1 <=> 1 //0
1 <=> 2 //-1
2 <=> 1 //1

Null Coalescing operator

$a = ['a' => 1, 'b' => 3];
$two = $a['2'] ?? '2';

Binary operators

And:

$a = 1;
$b = 2;
$a === 1 && $b === 2 //true if both are true
$a === 1 and $b === 3 //false if both are true, the change here is operator precedence

Not:

var_dump(!a) //false
//Or
$a === 1 || $b === 3 //true if any of expressions evaluate to true
$a === 2 or $b === 2 //true if any of expressions evaluate to true, the change here is operator precedence

Xor:

$a === 1 xor $b === 3 //true if only one of expressions evaluate to true
$a === 1 xor $b === 2 //false if only one of expressions evaluate to true, the change here is operator

Execution operators

Backticks:

$output = `ls -al`;
echo "<pre>$output</pre>";

Error control operators

x = @fopen("/tmp/foo"); //Ignore default error messages

String operators

Concatenation:

$a = 'Studing';
$b = 'ZCE';
echo $a .' '. $b;

Concatenating assignment:

$a = 'Studing';
$a .= ' ZCE';
echo $a;

Array operators

Union:

$a = ['one' => 1, 'two' => 2];
$b = ['one' => 2, 'two' => 4, 'three' => 3];
print_r($a + $b);
print_r($a += $b);

Equality:

$a = ['one' => '1', 'two' => 2];
$b = ['one' => 1, 'two' => 2];
print_($a == $b); //true
print_($a === $b); //false

Inequality:

$a = ['one' => '1', 'two' => 2];
$b = ['one' => 1, 'two' => 2];
print_($a != $b); //false
print_($a <> $b); //false

Non-indentity:

$a = ['one' => '1', 'two' => 2];
$b = ['one' => 1, 'two' => 2];
print_($a !== $b); //true

Type operators:

class A {}
class B extends A {}
class C {}
$b = new B;
$c = new C;
var_dump($b instanceof B); //Instance of A either B
var_dump($c instanceof A); //false

Control structures

If then else:

if (exp1) {
    //some code
} elseif (exp2) {
    //some code
} else {
    //some code
}

Nested if then else:

if ($omething) {
  //some code
  if ($somethingElse) {
    //some code
  } else {
    //some code
  }
} else {
  //some code
}

Ternary:

$queryParamsArray = (isset($_GET['q'])) ? explode('&', $_GET['q']) : false;
print_r($queryParamsArray);

Switch:

$a = ['one' => '1', 'two' => '2'];
switch ($a) {
  case 'one':
    # code...
    break;
  case 'two':
    # code...
    break;
  default:
    # code...
    break;
}

Foreach:

$a = ['one' => '1', 'two' => '2'];
//Lopp keys and values
foreach ($variable as $key => $value) {
  if ($key === 'one') {
    echo 'Exited on one';
    break;
  }
}
//Loop only values
foreach ($variable as $value) {
  # code...
}

For:

for ($i=0; $i < 10; $i++) { 
  if ($i === 6) {
    continue;
  }
    echo $i; //012345789
}

While:

$i = 1;
while ($i <= 10) {
  echo $i++;
}

Namespaces

This is better check files in Namespaces section