php.md

title	PHP
description	PHP cheatsheet contains useful code syntax with examples which is handy while coding.
created	2020-05-14
updated	2022-10-08

Basics

Sample Program

<?php
	echo "Hello, world!!!!"
?>

• echo : echo is used to output data to the console/screen.
• print : print is also used to output data to the screen. Both echo and print are more or less same with small differences, echo doesn't have a return value but print has a return value. echo can have multiple arguments but print takes only one argument. Echo is faster than print comparatively.
• fscanf : fscanf is used to read input from console
• // : single line comment
• # : Single line comment
• /* */ : Multi line comment

Data Types

PHP is a loosely typed language and hence you no need to declare variables with data types.

However, below are the different datatypes in PHP.

Data type	Usage
Integer	$x = 999999;
String	$str = "Hello World"
Float	$x = 79.53
Boolean	$isAvailable = TRUE;
Array	$arr = array("iPhone", 1000, TRUE);
Object	$obj = new className();
Null	$str = null;
Resource	$conn = mysqli_connect(localhost,"root","userName","password");

Variables

$variable_name = value;  

Constants

Using define()

define(name, value, case_insensitive)

• name: name of the constant
• value: value of the constant
• case_insensitive: Specifies whether the constant name should be case-insensitive or not. By default it is set to false.

define("GREETING","Hello you! How are you today?");
echo constant("GREETING");

Using const keyword

const MESSAGE = "Happy learning!";

String Functions

String Function	Usage
strlen()	echo strlen("One Compiler");
str_word_count()	echo str_word_count("Hello world! Happy Learning!!");
strrev()	echo strrev("One Compiler");
str_replace()	echo str_replace("bar", "Foo", "Good morning bar!");
strpos()	echo strpos("Hello world! Happy Learning!!", "appy");
str_repeat()	echo str_repeat("Hello! Happy Learning!!", 4);
rtrim()	echo rtrim(" Right space will be trimmed ");
ltrim()	echo rtrim(" left space will be trimmed ");
strcmp()	echo strcmp($string1,$string2);

Operators

Operator type	Description
Arithmetic Operator	+ , - , * , / , %, ++, --
comparision Operator	< , > , <= , >=, != , ==
Logical Operator	&& , ||, !
Assignment Operator	= , += , -= , *= , /= , %=
Conditional Operator	? :

Arrays

$arrName = array(values..);

1. Indexed arrays

$directions = array("East", "West", "North", "South");

2. Associative arrays

$capitals = array("Japan" => "Tokyo", "India" => "New Delhi","United Kingdom" => "London","United States" => "Washington, D.C.","China" => "Beijing");

3. Multi dimensional arrays

// two-dimensional array
$num = array(
  array(1,2,3),
  array(4,5,6),
  array(7,8,9)
  );

Conditional Statements

1. If

if(conditional-expression)
{
    //code
}

2. If-else

if(conditional-expression)
{
    //code
} else {
    //code
}

3. If-else-if

if(conditional-expression-1)
{
    //code
} else if(conditional-expression-2) {
    //code
} else if(conditional-expression-3) {
    //code
}
....
else {
    //code
}

4. Nested-If

if(conditional-expression-1) {    
     //code    
          if(conditional-expression-2) {  
             //code
             if(conditional-expression-3) {
                 //code
             }  
    }    
}

5. Switch

switch(conditional-expression){    
case value1:    
 //code    
 break;  //optional  
case value2:    
 //code    
 break;  //optional  
...    
    
default:     
 //code to be executed when all the above cases are not matched;    
} 

Loops

1. For

for(Initialization; Condition; Increment/decrement){  
//code  
} 

2. Foreach

foreach ($array as $value) {
  //code 
}

3. While

while(condition){  
//code 
}  

4. Do-while

do{  
//code 
}while(condition); 

Functions

function functionName() { // defining a function
  //code
}

functionName (parameters); //calling a function 

Date

(PHP 4, PHP 5, PHP 7, PHP 8)

date_default_timezone_set('America/Los_Angeles');// set default time zone( Useful while deploying to server)
$dateVal=date("F j, Y, g:i a"); // March 10, 2001, 5:16 pm

File

Function	Syntax	Description
readfile()	readfile(myfile.txt)	prints the contents of myfile.txt in browser
fopen(filename, mode)	fopen("myfile.txt", "r")	opens myfile.txt in read mode
fread(file, length)	fread($fptr, filesize("myfile.txt"))	read file upto length and stores in file pointer
fclose()	fclose($fptr)	The fclose() function closes an open file pointer

MySQLi Functions

These functions allow you to access MySQL database server.

Function	Description
mysqli_connect()	It opens a non-persistent MySQL connection
mysqli_affected_rows()	It returns the number of affected rows
mysqli_connect_error()	It shows the Error description for the connection error
mysqli_fetch_all()	It fetches all result rows as an array
mysqli_fetch_array()	It fetches a result row as an associative, a numeric array, or both
mysqli_fetch_assoc()	It fetches a result row as an associative array
mysqli_fetch_row()	It fetches one row from a result set and returns it as an enumerated array
mysqli_kill()	It kills a MySQL thread
mysqli_close()	It closes a database connection
mysqli_query()	It runs any sql query from database in php
mysqli_num_rows()	It counts number of rows affected after running any sql query

Global Variables - Superglobals

Variables	Usage
$_SERVER	$_SERVER['REQUEST_METHOD'] Returns the request method used to access the page (such as POST)
$_POST	$name = $_POST['fname'] collects value from a form(name='fname') and stores to $name after submitting an HTML form with method="post"
$_GET	$_GET can also collect data sent in the URL