Write text to the output using PHP
Keywords, classes, functions, and user-defined functions ARE NOT case-sensitive
Variable names ARE case-sensitive
Syntax for single-line comments
Syntax for multi-line comments
Using comments to leave out parts of the code
Create different variables
Test global scope (variable outside function)
Test local scope (variable inside function)
Use the global keyword to access a global variable from within a function
Use the $GLOBALS[] array to access a global variable from within a function
Use the static keyword to let a local variable not be deleted after execution of function
Display strings with the echo command
Display strings and variables with the echo command
Display strings with the print command
Display strings and variables with the print command
Get the length of a string - strlen()
Count the number of words in a string - str_word_count()
Reverse a string - strrev()
Search for a specific text within a string - strpos()
Replace text within a string - str_replace()
Check if the type of a variable is integer
Check if the type of a variable is float
Check if a numeric value is finite or infinite
Invalid calculation will return a NaN value
Check if a variable is numeric
Cast float and string to integer
Find the value of PI
Find the lowest and highest value in a list of arguments
Find the absolute (positive) value of a number
Find the square root of a number
Round a floating-point number to its nearest integer
Generate a random number
Generate a random number between 10 and 100
Case-sensitive constant name
Case-insensitive constant name
Create a Array constant with define()
Use a constant inside a function (when it is defined outside the function)
Arithmetic operator: Addition (+)
Arithmetic operator: Subtraction (-)
Arithmetic operator: Multiplication (*)
Arithmetic operator: Division (/)
Arithmetic operator: Modulus (%)
Assignment operator: x = y
Assignment operator: x += y
Assignment operator: x -= y
Assignment operator: x *= y
Assignment operator: x /= y
Assignment operator: x %= y
Comparison operator: Equal (==)
Comparison operator: Identical (===)
Comparison operator: Not equal (!=)
Comparison operator: Not equal (<>)
Comparison operator: Not identical (!==)
Comparison operator: Greater than (>)
Comparison operator: Less than (<)
Comparison operator: Greater than or equal (>=)
Comparison operator: Less than or equal (<=)
Comparison operator: Spaceship (<=>)
Increment operator: ++$x
Increment operator: $x++
Decrement operator: --$x
Decrement operator: $x--
Logical operator: and
Logical operator: or
Logical operator: xor
Logical operator: && (and)
Logical operator: || (or)
Logical operator: not
String operator: Concatenation of $txt1 and $txt2
String operator: Appends $txt2 to $txt1
Array operator: Union (+)
Array operator: Equality (==)
Array operator: Identity (===)
Array operator: Inequality (!=)
Array operator: Inequality (<>)
Array operator: Non-identity (!==)
Conditional assignment operator: Ternary (?:)
Conditional assignment: Null coalescing (??)
The if statement
The if...else statement
The if...elseif...else statement
The switch statement
The while loop
The do...while loop
Another do...while loop
The for loop
The foreach loop
The break statement in a loop
The continue statement in a loop
Create a function
Function with one argument
Function with two arguments
Function with default argument value
Function that returns a value
Return type declarations
Passing arguments by reference
Indexed arrays
count() - Return the length of an array
Loop through an indexed array
Associative arrays
Loop through an associative array
Output elements from a multidimensional array
Loop through a multidimensional array
sort() - Sort array in ascending alphabetical order
sort() - Sort array in ascending numerical order
rsort() - Sort array in descending alphabetical order
rsort() - Sort array in descending numerical order
asort() - Sort array in ascending order, according to value
ksort() - Sort array in ascending order, according to key
arsort() - Sort array in descending order, according to value
krsort() - Sort array in descending order, according to key
$GLOBAL - Used to access global variables from anywhere in the PHP script
$_SERVER - Holds information about headers, paths, and script locations
$_REQUEST - Used to collect data after submitting an HTML form
$_POST - Used to collect form data after submitting an HTML form. Also used to pass variables
$_GET - Collect data sent in the URL
Do a case-insensitive search for "w3schools" in a string
Do a case-insensitive count of the number of occurrences of "ain" in a string
Replace "Microsoft" with "W3Schools" in a string
PHP Form Validation
Format today's date in several ways
Automatically update the copyright year on your website
Output the current time (server time)
Set timezone, then output current time
Create a date and time from a number of parameters in mktime()
Create a date and time from the strtotime() function
Create more dates/times from strtotime()
Output the dates for the next six Saturdays
Output the number of days until 4th of July
Use include to include "footer.php" in a page
Use include to include "menu.php" in a page
Use include to include "vars.php" in a page
Use include to include a non-existing file
Use require to include a non-existing file
Use readfile() to read a file and write it to the output buffer
Use fopen(), fread(), and fclose() to open, read, and close a file
Use fgets() to read a single line from a file
Use feof() to read through a file, line by line, until end-of-file is reached
Use fgetc() to read a single character from a file
Create and retrieve a cookie
Modify a cookie value
Delete a cookie
Check if cookies are enabled
Start a session
Get session variable values
Get all session variable values
Modify a session variable
Destroy a session
Use filter_list() to list what the PHP filter extension offers
Sanitize a string
Validate an integer
Validate an integer that is 0
Validate an IP address
Sanitize and validate an email address
Sanitize and validate a URL
Encode an associative array into a JSON object
Decode JSON data into a PHP object
Access the values from a PHP object
Loop through the values of a PHP object
Throw an Exception
Use try..catch to show a message when an exception is thrown
Use finally
Output information about an exception that was thrown
Define a class and an object
Using the $this keyword
Using the instanceof keyword
Creating a constructor
Creating a destructor
Inheritance
Class constants
Abstract classes
Traits
Static method
Static property
Select data with MySQLi (Object-oriented)
Select data with MySQLi (Procedural)
Put the resut in an HTML table (Object-oriented)
Select data with PDO (+ Prepared statements)
Use simplexml_load_string() to read XML data from a string
Use simplexml_load_file() to read XML data from a file
Get node values
Get node values of specific elements
Get node values - loop
Get attribute values
Get attribute values - loop
Initialize an XML Expat parser, define some handlers, then parse an XML file