Statements

Control flow

if, else, elseif/else if

$number = 10;

if ($number > 0){
  print 'greater than zero';
} elseif ($number < 0) {
  print 'less than zero';
} else {
  print 'equal to zero';
}
//=> greater than zero

switch

$number1 = 10;
$number2 = 10;
$operator = '+'; // (+, -, *, /)
$result = 0;

switch ($operator) {
  case 'add':
  case '+':
    $result = $number1 + $number2;
    break;
  case '-':
    $result = $number1 - $number2;
    break;
  case '*':
    $result = $number1 * $number2;
    break;
  case '/':
    $result = $number1 / $number2;
    break;
  default:
    $result = 0;
}

var_dump($result); //=> int(20)

Iterations

for

$names = ['Alice', 'Bob', 'Charlie'];

for($index = 0; $index < sizeof($names); $index++){
  print($names[$index]."\n");
}
//=>
// Alice
// Bob
// Charlie

foreach

foreach (range(0, 9) as $number) {
  echo $number;
}
//=> 0123456789

$names = [
  0 => 'Alice',
  'admin' => 'Bob',
  'client' => 'Charlie'
];

foreach($names as $name){
  print($name."\n");
}
//=>
// Alice
// Bob
// Charlie

foreach($names as $key=>$name){
  print("$key => $name\n");
}
//=>
// 0 => Alice
// admin => Bob
// client => Charlie

while

$result = '';

while (strlen($result) < 4) {
  $result .= 'x';
  print "$result\n";
}
//=>
// x
// xx
// xxx
// xxxx

do…while

$result = '';

do {
  $result .= 'x';
  print "$result\n";
} while(strlen($result) < 4);
//=>
// x
// xx
// xxx
// xxxx

Alternative syntax

endif;, endwhile;, endfor;, endforeach;, or endswitch;:

$number = 10;

if ($number > 0):
  print 'greater than zero';
elseif ($number < 0):
  print 'less than zero';
else:
  print 'equal to zero';
endif;
//=> greater than zero

Includes

require()

Example 1

require
├── test.php
└── util.php

codes/require/util.php:

<?php
function sum($a, $b) {
  return $a + $b;
}
?>

codes/require/test.php:

<?php
include("util.php");

echo sum(1, 1);
?>

Example 2

require-path-child
├── lib
│   └── util.php
└── test.php

codes/require-path-child/lib/util.php:

<?php
function sum($a, $b) {
  return $a + $b;
}
?>

codes/require-path-child/test.php:

<?php
require("lib/util.php");

echo sum(1, 1);
?>

Example 3

require-path-parent
├── lib
│   └── util.php
└── src
    └── test.php

codes/require-path-parent/lib/util.php:

<?php
function sum($a, $b) {
  return $a + $b;
}
?>

codes/require-path-parent/src/test.php:

<?php
require(__DIR__."/../lib/util.php");

echo sum(1, 1);
?>

include()

include
├── test.php
└── util.php

codes/include/test.php:

<?php
require("util.php");

echo sum(1, 1);
?>

codes/include/util.php:

<?php
function sum($a, $b) {
  return $a + $b;
}
?>

require_once()

Error

require-error
├── lib
│   ├── math.php
│   └── util.php
└── test.php

codes/require-error/lib/math.php:

<?php
function sum($a, $b) {
  return $a + $b;
}
?>

codes/require-error/lib/util.php:

<?php
require("math.php");

function minus($a, $b) {
  return $a - $b;
}
?>

codes/require-error/test.php:

<?php
require("lib/util.php");
require("lib/math.php");

echo sum(1, 1);

// =>
// PHP Fatal error:  Cannot redeclare sum() (previously declared in 
// codes/require-error/lib/math.php:2) in 
// codes/require-error/lib/math.php on line 4
?>

Valid

require_once
├── lib
│   ├── math.php
│   └── util.php
└── test.php

codes/require_once/lib/math.php:

<?php
function sum($a, $b) {
  return $a + $b;
}
?>

codes/require_once/lib/util.php:

<?php
require_once("math.php");

function minus($a, $b) {
  return $a - $b;
}
?>

codes/require_once/test.php:

<?php
require_once("lib/util.php");
require_once("lib/math.php");

echo sum(1, 1);
?>

include_once()

include_once
├── lib
│   ├── math.php
│   └── util.php
└── test.php

codes/include_once/lib/math.php:

<?php
function sum($a, $b) {
  return $a + $b;
}
?>

codes/include_once/lib/util.php:

<?php
require_once("math.php");

function minus($a, $b) {
  return $a - $b;
}
?>

codes/include_once/test.php:

<?php
require_once("lib/util.php");
require_once("lib/math.php");

echo sum(1, 1);
?>